Of course you can generate large wordlists and run into storage problems however there is a bigger problem. Most applications in BT4 can only handle 2GB or less sized files. 2GB is the maximum filesize for 32-bit OSs. Yes there are workarounds (crunch uses them) but john the ripper and aircrack can't use a wordlist greater than 2GB in size. Then there is performance impact. To maximize performance you should have enough free RAM to store the wordlist in RAM. If you have a 2GB wordlist with 1GB of RAM performance will be horrible.