I think Rains did get a bit lazy acting wise after he left Warners in the late forties.

There are quite a few films where he is visibly bored and has just turned up for the paycheck. I suspect he lost the passion after a while and just decided to fund his farming lifestyle when he had too whilst doing the occassional desirable job for old friends (working with David Lean in Lawrence and Greatest Story Ever Told for example.)

Certainly, quite a few of his film choices seemed to be excuses to travel:-

The White Tower - climbing film with Glenn Ford, shot I think in Switzerland.

The Man Who Watched Trains Go By - France.

Even Lawrence may have been an excuse to go to Spain (where all the Damascus and military headquarters scenes were shot as I understand it.)