Unless your club runs are a series of all out efforts with short recovery periods between them, then 50:50 sessions of this duration are not what you ought to be doing really. A club run (i.e. Sunday club run, not a training ride) by my definition will be completed at a fairly steady pace and mostly aerobically, what you are training in is a fairly anaerobic region.
To ride "better" on long rides, you want to be riding for longer durations in your aerobic zone and to help with going a bit faster, as you might not want to sit on the turbo or rollers riding for lots of hours, you might like to try some tempo (up 90% FTP/lactate threshold/corresponding HR figure - around 85% max HR generally) rides of up to about 2 hours or some sweet spot training, (sub-threshold, i.e. about 95% of your FTP/lactate limit/corresponding HR figure - high 80's% closing in on 90% max HR) intervals of 20-30 mins or so with a 10 min rest in between.
Don't under estimate the effort required to ride tempo for 2 hours, it is hard graft, might not seem hard at 1st but as the clock ticks, it will get progressively more uncomfortable, so don't over do it at the start, get your HR up to about 85% max and then sit there for 2 hours.
Both the tempo and sub-threshold zones are very good bang for your buck in terms of all round performance and will help to increase FTP.
but would be quite happy to set a nice steady pace on the club runs, charity events etc in this coming year and see if i could up the mileage from last year!
