in Germany a trailer is not really an option as motorcycles with trailers are limited to a max speed of 60 km/h (37,5 mph) so only very few are in use over here, mainly with the Goldwing community.
We do trips up to 4 weeks two up and when we do so one saddlebag is for spare parts and tools only, the other one contains spare clothes, tour pack is empty and reserved for helmets, zumo, jackets on stopovers or a really hot day and all other luggage including pc is in the bag. Usually once in a week we find a friendly hotel doing the laundry overnight and after around 2 weeks we send back some of it by mail as we usually buy some t-shirts and other stuff here or there. Still we always bring back some unused t-shirts so evidently could pack even less
We use all weather gear on those trips and that's comfortable between 25 and 95°F (more or less
).