While on the California Melee in a friend's '55 TR2 (on a backwoods dirt road up in the mountains and very far from a parts store or towing location), we had a rock thrown up by the front wheels put a hole in the thin metal side of a spin-on conversion filter element, causing an oil leak that would have gradually emptied the sump of most of its oil. And, even if somehow we noticed the leak before the oil pressure went catastrophically low, we didn't have a spare filter and six quarts on oil on board (silly us...).
Fortunately, we soon ran (softly) down off the road into a leaf covered dirt embankment, and the leak was noticed while 7 or 8 other rally participants were helping us lift the front end of the car back up onto the road. With donated extra oil, we were able to make it the 30 or 40 miles to the NAPA store down in Garberville just before closing and bought supplies - though it meant abandoning the rally route for the remainder of the day.
When I got home, the spin-on adapters came off of my two TRs, and I've removed them from 2 or 3 TRs and a Morgan owned since then. The stock Triumph filter housing is around 1/16" thick and much less vulnerable to road damage. It it leaks, new rubber seals are available, or the center bolt can be tightened. A "stubby" 9/16" ratcheting "gearwrench" (or similar, available at FLAP store) makes it easier to loosen or tighten the housing bolt, and the wrench can live in the glovebox with your corkscrew and church key.
Standard-Triumph engineers knew what they were doing when the specified the sturdy original oil filter housing....