I been riding the same old shovelhead for alot of years. Have used just about every type of oil out there at one time or another. Had to rebuild the top end once(main problem valves), but I beleive gas changes over the years caused that. Any way, the key thing is to keep the guts clean with regular changes. How often? That depends on alot of deferent things(like how hard ya push the bike, dusty riding conditions, etc.) Pick a number between 2 & 5 and stick to it.
P.S. Here lately been using Mobil-1 15W50 snyth in the engine, but still use straight 60 in the tranny.
Ed