They’re fine as is. Only thing I might do is tape over the jacks or any holes to keep dust/ creatures out. If it’s in an enclosed container maybe some desiccant packs
Electrolytic caps "degrade" over time if not used. Turning the amp on for 20min (you don`t have to play it) every 6 months prevents this. Other than that, keep the amp in a not to humid environment.