OK, I do live downtown and am surrounded by bike docks (at last!) but I use Bike Share quite a lot (walk one way, bike home) and have been a Member since before the launch and I have never had any overage fees. This may be due to my Ulster protestant roots and my (generally!) frugal ways but my partner also has never paid overage either. Of course, 45 minutes might be handy occasionally but if it cost more in membership I would 'vote' no. You can avoid overage fees if you keep an eye on the time and, if necessary, dock your bike and then start again.
I've never had overage when I used the service in downtown Toronto either.
But now that bike share has expanded to Midtown, the station docks are less frequent, and the destinations reachable by bike farther part, I've hit the overage quite a few times this summer.
Perhaps it can be resolved by greater density of stations, but it's still rather inconvenient if on my way downtown from let's say, Lawrence, I would have to find a dock in Rosedale, and re-borrow my own bike in order to complete the last ten minutes of my journey. You're out of luck too if you don't have an annual pass.
To grow the service, I believe it needs to be as convenient to use to as many demographics as possible. It might be possible to one-shot the above-mentioned trip if you are an able-bodied 20-something male with high-risk tolerance and were to shoot down Mt. Pleasant, but if you aren't in that narrow demographic, or have to take detours and side streets for whatever reason, then that 30-35-ish minute trip can easily be an hour.
Ultimately, I think a 45-minute window grants greater freedom to users to use the service as convenient to them, and I think that is a good way to grow service usage now that the proof of concept is proven (in downtown) and the objective moving forward seems to be expanding service coverage across the city.