Received an invite sometime last year... But ignored it... And just got another invite from NW again... And since my NW has been in active for a long long time... I thot why not... Gathered 300+ points so far... Hopefully, that will keep the NW account going...

Sidetrack a little... Is there a summary on the policy enforce by different FF programs regarding inactive account?

I know SQ's miles would expire, UA would requires activities within a timeframe of 18 month to prevent miles from expiring, and NW seems to be the only one that just keep going and going like the energizer rabbit.