Valve caps are not something I worry about. If I have a suitable set, I will fit them but if I haven't, then I do without. I have seen the mushrooming effect of not using the caps - but that was around 50 years ago on a head taken out of service some time earlier. On my own machines I have had no problems resulting from not using them.
36 4G, 37 VH, 54 KH(A), 75 Healey 1000/4, 52/53 ex ISDT KHA (project).
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist once more - but not Machine Registrar.