I use digital envelope budgeting by creating subaccounts in gnucash and allocating my income between the subaccounts every month.
Some expenses are relatively constant every month. Examples are groceries, electricity, internet, telephony, magazine subscriptions, and of course rent.
Other expenses vary between months, but are relatively constant year to year. Example are heating, holidays, license fees, and subscriptions that are charged yearly.
But others yet are even more occasional. I might go several years without buying furniture, then at some point I might replace the fridge, buy a dishwasher and a new sofa. I find it difficult to know how much money to put in the envelopes covering those categories, but that is not my question here.
I've seen websites recommend that the envelopes should be emptied every month, but that doesn't seem useful for something like holidays, where I might spend many months spending 0 and then one month spending more than €1000. On the other end, if I don't empty them at all, the amount in some categories just accumulates over time, which might not be very useful either.
What should I do with money left in envelopes (subaccounts) at the end of the month or year? Should I clear them at all, if yes, how often?