ORIGINAL: greekmath
The only thing is you can't “re bush” the engines cheaply so once they are done they are done.
Not really an issue when using the correct fuel.
A bronze bushing can last for several hundreds of hours if there's enough castor in the fuel. I've got a late 1950's vintage Fox .29 that easily has several hundred hours on it. The bushing play is still perfectly acceptable, and compression is still good enough to flick it by hand and get one-flip starts.