Note: I design solar powered LED based lighting products (amongst other things).
Manufacturers can be expected to rate such LEDs to last well in excess of the expected life of the camera.
LED lifetimes for small LEDs are usually less or MUCH less than the lifetimes quoted for power LEDs for a range of reasons.
And manufacturers can choose to drive them hard enough to much reduce lifetimes - in a focus lamp application I would not be surprised if a manufacturer did chhose to significantly over drive the LED above normal ratings. In many contexts an LED lifetime of 1,000 operating hours or even less would be much more common than people realise. But, if you sum the actual operating time of a focus assist LED it will be well under 1000 hours for the most enthusiastic use over decades of use. Even a 100 hour lifetime would be enough for all but the most flash-happy of photographers.
If the assist lamp operates for say 2 seconds then even only 100 hours of use would give you 180,000 operations.
Over 10 years that is 50 focus-lamp-assisted photos every day.
[ 100 hours x 3600 seconds/hr / 2 seconds per use / [10 years x 365 days) = 49.315 = 50 / day.]