'99 RangeRover 4.0 Oil Leak

[Master-Teq]

Hi All,

My RangeRover has always been clean with no oil leaks. I then had to go overseas for 6 months.
When I returned, I noticed a puddle of oil under my RangeRover.
I went to the local Landy agents and they quoted me on a rear main oil seal and a breather valve.
My question is: How can these things just start leaking when standing still?
Can any one please clarify this for me?

 

[joey]

Its a Rover if it doesn't leak, it has either had all of its seals replaced or it is out of oil.