Here's a long explanation: You usually can vandalize four times without being blocked, sometimes more if they don't catch you or if you vandalize too quickly to be caught, and sometimes less if they're feeling a bit impatient or your vandalism is really bad (severe BLP violations, etc.). If you vandalize again after getting the fourth and "last warning" on your talk page, they'll report you to AIV and block your account or IP address. This means you can't edit Wikipedia from that account or IP address. Now if it's an account, and pretty much the only thing you've been doing is vandalizing, then the account is usually blocked forever. If you've done significant good things with the account, however, you might only be blocked temporarily (e.g. 24 hours, 2 weeks, etc.). But if it's an IP address, the block will never be permanent, always temporary (because IP addresses change eventually). They do not, however, "delete" accounts, just permanent blocks.
Yes, you can make a new account or even just log out and edit as an IP, but sometimes this is temporarily prevented in a form of an "autoblock". When you do make a new account, if you keep vandalizing the same way you've been doing, they might pick up on it, launch a "sockpuppet investigation", and block all accounts made from your IP address. The trick is to make it seem like you're a totally different person so they don't get suspicious. If you keep making a bunch of new accounts and they keep catching them as sockpuppets, then they may eventually contact your Internet Service Provider (Verizon, Comcast, etc.) and ask the company to investigate your behavior and do something about it, BUT this is very rare and only happens if they're really getting tired, like maybe you've been going on for many months.
Three things to keep in mind: 1. They can never prevent your vandalizing, only make it harder, as it's just a matter of going to another location and vandalizing from that address. 2. There's nothing illegal about vandalizing Wikipedia, you won't get in legal trouble for doing so (except for death threats, etc.). 3. But, vandalizing Wikipedia is mean and pointless, and you should stop doing it. :)
I used to have over 9000 abusive sockpuppets. Now I revert vandalism everyday.