Its a coolant to oil heat exchanger. I can't imagine it ever needing replacement unless it has physical damage.
The engine is running normal temperature at the time?
Considering the conditions you are running in, maybe a larger aftermarket air cooler would be of help.
And maybe new transmission fluid including flushing the lines would also help. I'd also change your differential and transfer case fluids more often.

If you do remove the cooler to clean it, you HAVE to replace the sealing rings else they will leak.

Also, you don't have your vehicle in your sig, so nobody will know which engine/transmission you have without knowing the model year of your X5.

__________________
*********************
Olympic Peninsula, WA, USA
-----------------------------------------
2005 Mini Cooper 100k, British Racing Green/Silver-Black
04/2002 4.6is 140k, Silver/Black-Alcantara *FOR SALE*
1989 325iX 270k, Diamond Black/Black
1984 318i 370k *SOLD* (First Bimmer)
Honorable Mentions: '71 2002, '87 325, '90 325ic, '92 525it, '93 325i, '94 530i