With the scenario you describe, you are doing exceptionally well !
(I make that comment assuming you have no debt (car, credit card, etc); if you do, then pay it down forthwith and
then you're doing exceptionally well
)
People tend to castigate themselves about cash in the bank. It's true that at typical tax rates, cash at bank is going steadily backwards. It's not accruing value; it's shedding value. Bit by bit, year after year, cash at bank erodes away (after tax).
So does that necessarily mean it's a bad thing? No.
Cash at bank is like buying insurance. It costs you. Each and every year it costs you money. But the goal is to avoid a possible larger loss.
So don't think in terms of "it's only making me 4%"; think in terms of "it's
costing me 0.5%, but it's a worthwhile insurance premium".
It's not a good strategy for a 20 year or 50 year time-frame, but over small time-frames it can be a good insurance policy to purchase.