Durable speed sails

Avanti look pretty durable.
Not much monofilm

avantisails.com/17-sails/machine-m4/

there's the conundrum.
fork out more and not renew so often.
or go for mono sails and upgrade every season or so.

I currently Sail Avanti - They are bullet proof and very light - currently on the M3's but have used the M1x's for 3 seasons and were still in great condition. Only updated to get a better shape/twist.
They are expensive but will outlast anything else on the market by years..

Unfortunately there's no aussie dealer atm (can order direct from europe with free delivery though) but I sail 2011 (6.3, 7.8) & 2012 (7.0, 8.8) Loft Blades. Pretty much bullet proof although 2015 models went all mono film under the guise that "monofilm" is faster (bullsh1t meter going off the scale). GPSTC sailing open ocean can be pretty demanding on gear and these sails have been through the wringer.

If I ever replace my Lofts it'll probably be KA koncepts/race as they're now primarily x-ply construction. Those avanti do seem incredibly tough too.

My 2015 KA Races still look great

I've been windsurfing short boards since 1983, raced Stroh's World Cups against the Europeans for 3 years, won a few local surf slalom races, and competed in Speed Trials for years, a long time ago.
I always thought sails actually made a difference.
But I was wrong.
I've been biased against Ezzy sails because I'd never seen an Ezzy sailor I couldn't easily pass, whether the same size, a meter smaller, or a meter bigger. Then I picked up a used '04 Ezzy Infinity 6.6.
It's as fast as any sail ever made, and that's comparing it to new (at least '14) sails with full on slalom kit, me on fast freeride. For the same winds, it might not have the same low end, so I rig it with less downhaul, but it's every bit as fast as my Norths, Gaastra's (including '17 Cosmic 6.7), Lofts, Simmers, or Neil Prydes.

Sorry.
I"m old, got to live a lot of year's, 67, and tried a bunch of things, never getting good at any.
Didn't have to work too much, so just did sports.
Like, owned and raced over 15 motocross bikes.
Raced a YDS-3C, Suzuki X-6, and a TD-2 for a couple years. AFM and CME road racing. That led directly to a job with Team Yamaha.
Surfed full time for 26 years.
Been sailing short boards since '83, Seatrend Team Rider from '85 thru '89.
Snowboarded over 400 days, starting late, but because I went to trade shows and worked at a shop, rode with some of the better riders.
Waterskiied over 100 days, maybe 10 with some pros in practice.
Even qualified to try out for a pro tennis tournament, but lost in the 2nd round of Q.
Ask your grand dad. I'll bet you'd be surprised all the things he did that you didn't know about.

Good to hear, when other brands have gone light it has resulted in poor quality including some brands issuing their team riders several sets of sails. One such brand i broke the bit of spaghetti they call a batten today just flipping sail in water, not something ive done in 25+ years of sailing.

Sure, you can compare rec. Ezzy's to full on slalom race sails. It's a sail after all, something to propel you on your way.
I sail with guys on the newest slalom gear all the time, at least within 2 years anyways, and I use freeride kit, so it's an easy comparison. My Ezzy is a '04 model Infinity 6.6. My newest sail is 2017 Gaastra Cosmic 6.7. Most of the guys I sail with use within 3 year old slalom race sails.
The relative speeds don't change just because you're using a old model Ezzy. Now in a real organized slalom race, it would, but that's assuming 5 minute heats, 3 sails rigged on the beach, and short reach's with 8 jibes. Freesailing is not the same thing. Freesailing is sailing for 2 hours, for whatever distance the wind and circumstances allow, is is more a matching up of top speeds rather than just start/jibing skills.

the last few years I've needed to keep my windsurfing costs as low as reasonably possible. so I have held into my last set of sails for a while. I've stuck with north warps since 2004 (F2004, F2006, F2009, F2010 and F2012), mainly stuck with Norths because I gave a full set if North vipers/platinums masts and dont fancy folking out for another full set if masts.

All the north Warps I've had have been bought secondhand. North always seemed to use thick monofilm and decent luff tube material. I recently gof a F2013 9.6m and the monofilm was much much thinner than my F2010 9.5m. The main panel ripped after just three sessions. Luckily I still got my old F2010 9.5m so I'm back using it now.

tomorrow, im getting a F2014 7.8m, it'll be interesting to see if the monofilm is super thin like the F2013 9.6m. Hopefully North have gone back to thicker monofilm like on my older warps.

are all sail manufactures using thinner monofilm these days? I'm guessing saving weight is their priority!!

Seems every couple of year's, a new monofilm supplier make's it's way to the windsurfing tradeshows, promising increase life, imperviousness to UV, but at a slight increase in cost per foot per gauge (thickness).
So, the manufacturers are always looking for improvements, buy the technology, but try to save costs of more expensive materials by going thinner.
Or, the monofilm supplier promises that their new thinner monofilm will outlast the old thicker monofilm.
I remember Neil Prydes attempt at thin 4 mil mono, around 1990, when the film appeared more pliable and clear than any before it, when new, but quickly aged to a crackled, dull, clouded , and worn out material within 50 days of usage.
I wonder if the newst 4 mil is any better? I have a '17 Gaastra Cosmic 6.7 that has 17 days of usage now, so will be checking it closely. Unfortunately, no answer will be coming soon, as the windsurfing season around here ended a week or so ago.