I'm like you, "I don't like wasting money on premature replacements." So I would keep riding them. But I know other people who would change those tires in a heartbeat. It's all a matter of personal comfort level.

I say pump 'em up good, get on the bike, jump up and down real hard on the pedals, maybe intentionally ride over some stiff bumps, jump off some curbs, and if they don't asplode, ride with peace of mind.