As has been said there isn't really a cut off point to note, weather dependant really. I'll probably leave them in the cupboard from April/May but I've never really thought about it. I've got Pro Tarmac NPU for the 'oribble rides and Castelli Toe Thingys for when its just a bit chilly. Never found the Tarmacs difficult to get on and they're quite thick, turning them inside out then peeling them on and zipping up takes about 5 seconds. To be honest even if they took 5 minutes to get on it would be worth it, nothing worse than cold wet feet for 3 hours on the commute.