Anything that causes a seal to swell also makes it softer, which means it will wear out faster. So you have not only oil in the exhaust; you also have this snake-oil in the motor oil, along with seal residue.

Better to just do it right the 1st time: replace the seals. It takes a special tool to compress the valve spring, but the price on it has come down from ~$100 to ~$30. There was a thread about it maybe a month ago.
Walk softly & carry a BIG SIX ! ! !

. . .