How long does a professional spray-on tan last for?

Eg from beauty salon? Was going to Thailand for 10 days and look v nasty pasty white :) Also does it help cover up stretch marks etc? or should I save my money and go solarium style?How long does a professional spray-on tan last for?
Solarium takes a fair few sessions to get brown. And it is terrible for your skin. I suggest get a spray tan the day before you go, and the morning you leave have a shower. If you dont have time for a shower, then get the spray tan 2 days before you leave and shower the day you leave. You have to wait about 12 hours before you shower. Also , before you go to the salon, make sure you exfoliate your whole body and shave your legs, etc so your skin is smooth. The colour will last longer. Also moisterise every day whilst away to keep the colour fresh and the skin smooth. They are supposed to last 2 weeks, but after about 10 days they start to fade. So i would definilty recommend getting a spray tan over solarium! Get to a good one though that wont make you go bright orange, Ask friends for recommendations for salons! Good luck, you will look tanned and fabulous for your holiday!