Adsense only allows one Adsense account per person so you won't be able to have multiple Adsense accounts because if you do you'll eventually get all the Adsense accounts banned.
You can safely use one Adsense account on multiple websites without a problem as long as the websites comply with Adsense Terms of service and you don't do any click fraud or do anything else that is against Adsense Terms of service then your account should be fine for years to come.