How often have any of you seen the front crankshaft seal leak?

I don't think I have a leak, but I just want to make sure since I will be replacing the valve cover gasket and the timing chain cover gasket and if there is a possibility that it could leak in the near future, I want to go ahead and replace the front crankshaft seal.

Vehicle: '86 300E
Engine: M103
Miles: 112000

Thank you.

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1986 300E (3/2002) Rear ended and totaled (10/2009)
2000 Xterra (5/2000)
1992 400E (11/2009) -Sold
1986 300E (12/2009) - Sold
2004 E500 Wagon (6/2013) - Sold