engine exhaust valve rotators

If you're going to have the head off anyway, having the head cut and seat inserts installed should only cost around $20 a seat. Not a big deal in the long haul.

Unleaded fuel isnt' something you'd notice with occasional or light use, but over the long run, and/or with some hard use, it does.

You might already have seats installed anyway, if it's had professional valve work done before.

I wouldn't do a valve job on anything without installing exhaust seats unless it was a machine that was strictly for show and never really got used. Also, if a flathead - I often don't do it since to do so - would require pulling the engine and bringing the whole block to the machine shop.
I just got done fixing up an Oliver Cletrac dozer with a Hercules IXB, valves-in-block engine and the seats were worn something awful. It needed seats badly, but I refused to pull the engine out. So, I ground them extremely deep and am now using a gas-additive. That because I really use the little dozer for pushing dirt in tight places and it needs all the help it can get. It should of had seat-inserts - but I was too cheap.

I realize that a lot of this older stuff does NOT get used hard anymore - so, it's a personal choice. I use most of my older machines for real work. I don't mind spending an extra $40-$100 on seats knowing that it will make a valve-job last much longer (as long as it's valve-in-head engines). Seems many people have forgotten (or weren't around) when cars and trucks got routine "carbon and valve jobs" every 80K miles.
Farm tractors also got them often - miles and/or ours unknown. It's pretty much unheard of today. That because #1 unleaded gas leaves less deposits, and #2 all the heads have hard seats now. Ironically, it's the lead-oxide deposits that leaded gas used to leave that protected seats from wearing out - until it built up so much it could hold valves open enough to leak. One of the purposes of valve-rotators was to spin the valves a bit that made them self-cleaning.

Thanks for the reply.

I may of misread your original question ? Yes rotators ARE for better durabilty. BUT I seriously doubt you will ever notice the difference even if you run it hard on this tractor. I think I tore one down once that had them on all four valves.

And actually the exhaust valves don't have as much problems as the intakes. I have had alot more intake valves on 2 cyl. tractors not survive the grinding. They seem to get more hammered up faces. Also the intake stems get more wear from dirt in the air so check the stem wear too.