There is no publicly available data on the longevity of seals by Tesla or any of its suppliers. So what is the best seal and how long will it last? Nobody knows, so this page attempts to create an overview of individual's seal replacement experiences.
Other sources:
A rule of thumb for the life expectancy of the triple lip seal used at QC Charge is "twice the LDU's mileage before the rebuild". So for example, if your current LDUran 30k miles at the time of seal replacement, then the LDU is estimated to run another 60k miles on the new seal. But it also depends on driving behaviour, climate,etc. According to QCC, the mileage till a leak on an original Tesla seal ranges from 20 to 150k mi, typically 60-80k mi.
Early LDU failure statistics @ greencarreports
Early (2014) LDU failure discussion @ EVTV (coolant leak not mentioned but maybe related)
An exceptional case with 13 LDUs over 1000k mi = 77k mi /LDU @ youtube (guy drives "only" 100km/h = 62mph on highway during the night 12:55 hh:mm)
(Legal data point from Tesla Warranty: "Drive Unit*: 4 years or 50,000 miles, whichever comes fi rst". This sais something about how much risk Tesla (and possibly their insurance comany) is willing to take / what Tesla pays insurance premium for. Found here.