I don't think the X5 is any different than any other modern BMW vehicle.

If it functions as designed, there are no issues at all with leaving it for two weeks. I have had four BMW vehicles in recent history, all have been parked regularly for 2-3 weeks, never had an issue. The 5 series was left up to 4 weeks regularly.

If you have a small parasitic power drain, then the vehicle doesn't go to sleep as it is designed to, and you end up with a flat battery. It can be tough to diagnose. Some owners and/or dealers have given up on specific vehicles, and just gone to using a battery tender out of either necessity or an overabundance of caution.

So, you may have a problem. But if so, it isn't because it is an X5 50. And any other BMW could have the same problem.

I don't have a 50i. But I have owned and driven several different recent turbocharged BMW models. None exhibited turbo lag. All had some degree of tip-in delay, to various degrees, depending on the engine model. None of them had it enough to bother me at all.

__________________
2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue