I used to do very long distances in my Minis and am hoping to do so again. I used only Castrol GTX, changed every 6000, which gave an engine life (standard 998) of over 100k miles. (I would use Miller's special oil for Minis now.) I think that because very few short journeys were involved, the oil lasted longer, same as with any car. Plugs and points every 12k, sometimes plugs at 6k, as one brand did not last very well, I think it was Bosch.
Gearboxes, except one which failed spectacularly, and one failed input shaft bearing, needed negligible attention, except for rod change oil seals, before the mod kit was introduced. Probably changed about once a year.
Pot joints, just checked every 6000, they rarely needed replacement. CVs also checked while greasing, every 2000, but typically lasted about 80k miles.
I did grease regularly, every 2000 miles or so, and ball joint replacement (after the first time) was very rare. Radius arm bearings went on almost for ever, I only changed them once, on the first van, which had been neglected and was cheap. Knuckle joints every 60k approximately.
Brake fluid changed rigorously every 18 months, and all seals every 3 years. Drum brakes adjusted every 2000, at the same time as greasing and CV inspection, or when the pedal travel suggested it was needed. Drums off every year or so, to inspect linings and check for leakage.
I did tend to have the head off every 20k to 30k miles to decoke, grind the vales, fit new valve springs, and check for bore wear. New bypass hose fitted every time.
The biggest problem was the constant battle against rust, however with modern paints and decent restoration practices that can be greatly reduced.
