I have one of those Bangood bottom and top bearing flush trim bits. It was cheap as chips and I thought if it does not last long I'll just get another. It has turned out to be pretty good and has a ton of use and still gives a reasonable finish. Who'd have thought? I've had one of those Whiteside two bearing spiral flush trim bits for a while but it has not had much use because it is a bit chunky, and vibrates dangerously in my aging Ryobi which has naff bearings. I thought I'd got a dud but tried it in the TRA001 at my Menz Shed and it was fine. It had it's first proper use today when my Bosch 1600CE arrived, and produced an excellent finish on some rimu.
Other than that, I have a number of bits from Bunnings and Mitre10, and big box of bits from The Toolshed, and so long as they are cleaned now and again, they seem to last forever. I suppose I do freshen the flat edges with a diamond plate now and again.
When I think about it, that single Whiteside bit cost more than all my other bits put together, and by a significant margin.