Mine has well over 500 hours on it and shows no sign of a problem. That's not counting the times when my kids just leave in on all night long. It seems to be a durable machine. I'd just make sure to keep it well ventilated and blast some canned air in the air on occasion - just in case.
They'd have to do something totally awesome to Lemmings for me to buy it. I imagine some developer would put it out there to make an easy buck with no genuine concern for the game - or any inovation for that matter. You never know though.
I'd go with the Zone Alrm free firewall, keep your AVG for a "constant resident shield scanner" and then get BitDefender Free. The free Bitdefender does not constantly scan but works awesome as a "on-demand" scanner. This combination works well and is free.