This is Keynes argument against Demurrage Currency, the fees can be evaded by using a competing currency. When demurrage has been used successfully in the past, the main competing currency has been broken (30's Austria, depression era USA)

Nothing, in fact that is encouraged. I could imagine having a “checking account” in demurrage currency that my paycheck is deposited into, but at the end of the week or month I sweep excess funds (my savings) into a “savings account” backed by treasury bonds, gold, bitcoin, or similar.

The point is to keep cash itself in circulation, regardless of economic circumstances. Had we a demurrage currency in 2008, we might not have had as severe a “credit crunch” as we did--people would still want to loan or invest even in bad times. Demurrage removes, through negative incentive, the “sinks” where money can end up in unproductive storage on the ledger of some company or individual somewhere, and instead keeps it flowing through the economy.