>>1017440I've just got a single 48L pack. An Osprey Kestrel I bought years ago.
I use it for everything. It compresses down small and comfortably enough when I'm just doing day trips and stuff that I never feel like I need a smaller pack. I use it for commuting and picking up groceries and stuff on my motorcycle too.
On trips longer than 3 days or so, it can get filled up quick, but it's easy to relocate some stuff to the outside of the pack when needed, and it's amazing how much shit you can cram into it if you really need to. Definitely more weight than I want to carry anyway.
I've never felt like having a larger pack would have made things any easier really.