The problem with most (seal) leaks is the seals are not very good quality being made to a price rather than a quality.
Where ever you can use VITON as it is much more suited to HOT applications such as engines, normal oe seals last ok but VITON outlast them easily, but are MORE EXPENSIVE.
Bt the time I had bought 1 crank(front), 1 auxillary shaft, 2 x cam seals I had no change out of £45, but then this is roughly the cost of 5 litres of decent synthetic oil so worth it IMO.
tabetha