The Welsh Highland could probably do with another two, but IMHO would probably welcome all of them, since with one being rebuilt by a benefactor there is only one still remaining in store, and that has already donated parts to the others.
Don't forget these locos in high summer are making two return trips a day @ 50 miles each return trip so are at a guess covering maybe 300 miles a week, plus whatever is needed for specials and charters (it's become quite popular for local organisations to hire a whole train for an evening fund raising ride and meal).
Bob Gartside