Worth it to balance rotating assembly?

OOPS I forgot to say the important bit!

The out of balance is felt at approx 1500, 3000 and 6000+ rpms

Its got nothing to do with the maximum rpm, its happens several times in the rpm range.

If its worse at 3000, then when you are cruising the bearings will get destroyed...

Around town you go 'up and down' past the problem areas without really noticing it?