Don't think of life spam. It will be modified. Domain name may be changed. But the idea remain active.
nothing lasts forever but I would predict it will remain on the web for some time to come, much more reliable than other advertising networks.
Of course, AdSense is here to stay. It is the main revenue generator for Google so there is no way Google will close for a few years at least or maybe forever.
If Google keeps getting much profit as its getting now from Adsense, then they will surely keep it going as it is now ! - Digital -
I find no reason why AdSense would not stay. Modifications may be applied but AdSense in my opinion will stay there for as much as it takes.
Yea, Adsense might stay around for the next few decades BUT it will definitely receive some big updates along the way and constantly be improved. I think as long as the internet is around there will be advertising, and as long as there is advertising there will be adsense or AT THE LEAST some program that makes you money from posting ads on your website. so no worries although that doesn't mean you should just rely on adsense, once you begin earning with adsense start to also focus on other methods of making money online to be safe.
It's probably not that Adsense will stay for life. But, I am sure if Adsense fails, other companies will rise.
Marketing is everything for a company. One way or the other, there will always be a possible to earn income from online marketing.