Stop bath and fixer keep a long time as unused concentrates. Film developer keeps less well, the exception being Rodinal, not ideal in every respect (lots of grain), but the concentrate keeps almost indefinitely. Film developer is not that expensive, throwing away leftover time-expired concentrate will not break the bank.
35mm scanner? I would say simply - the best Nikon Coolscan you can find secondhand (probably a III, maybe a IV).
Not all film chemistry has a short life, I use Pyrocat HD which I make up myself and that keeps well over a year, much longer if I used the Glycol version. Ilfotec HC or LC has a long shelf life even part used, so does Rodinal.
Your scanner question is best asked on APUG sister site Hybridphoto.com