When you install LFS it's installed as demo licence level. You then use your account details to unlock it so that the installation is linked to your account and licence level (S2 in your case). You can then start that installation as many times as you like, and join as many servers as you like - no limits.
You should only need to unlock it again if you re-install it or want to change users, not every time you use it. You get 3 unlocks initially, plus you get one more each Friday if you have less than 3 left. You can also email the devs to get the count reset if you explain your situation.
Are you running it in some kind of sandbox/emulator? If so I can't help with setting that up, but somebody else might be able to if you list the software you use.
Or maybe you're swapping back and forth between two accounts? If so, install two copies and unlock each one to a different user, then run the installation for the user you want each time.