I can't comment on freezing. Kodak officially says that XTOL lasts up to 6 months in sealed bottles, and most people report the practical limit is likely to be greater than this (probably a year or more), but XTOL doesn't change color when it goes bad, so keeping it for a long time can be risky.
If you like XTOL but you can't use 5 liters of it in 6-12 months, you might consider using a mix-it-yourself XTOL-like developer, such as
Mytol. You can then mix it in whatever quantity you like -- even fresh from raw chemicals for a single roll. (You might need to prepare a stock solution of phenidone in propylene glycol to make it practical to measure the small quantities of phenidone you'd need for this, though.) Of course, the mix-it-yourself approach will require you to buy some raw ingredients (Mytol requires five, plus water) and a scale. If you buy a few more ingredients you'll be able to experiment with other mix-it-yourself developers, though.