I recently fitted some of these 6500k LED festoon bulbs:-
https://www.amazon.co.uk/Keiurot-Fes...1zcF9hdGY&th=1
They provide a good super bright white light and I am very impressed with them.
You will need to order 36mm for a 2016 XC60.
Care needs to be taken when installing the bulb holders back into the recesses as they're a snug fit and the bulbs can easily twist if the heat sinks catch the sides. I had to re-install mine a number of times until I got them right.
As far as longevity is concerned, I can't comment as I only installed them a couple of weeks ago.