Personally, I don't believe in all the unleaded / valve seat hype. Years ago, a certain someone in the U.K. probably made lots of money by cashing in on the 'fear factor', when leaded petrol ceased to be available over here. Some of the adverts for unleaded valve seats were terrifying and made you think 'perhaps I'd better pull over in the layby and get the head off right now'. It was roundabout the time I had my Trident upgraded to 850 cc by Norman Hyde, who also had my cylinder head in for an upgrade. Upon enquiring if I should have unleaded valve seats fitted, his reply went along the lines of 'you could if you want, but we don't see the need for 'normal use' and are just monitoring the situation at present, if you don't get any valve seat reccession in the first couple of thousand miles, it should be ok'. I did over 8,000 miles with no change in the valve clearences and I wasn't gentle with it, either. [I had to put it away because I had a family starting and fuel was [and still is] very expensive and Tridents are thirsty beasts, one day, though].
Many old British bikes [and others], as well as other machinery, had to run on all sorts of muck during and after WW2 and they survived ok, with many still around today.
I think I still have a can of octane booster around somewhere, a left over from when our racers used petrol / avgas mix and unused since.
If you want to have unleaded valve seats and / or additives etc, go for it, but I don't buy them myself.
B.W.