If I'm not mistaken, your account will become computerized (a bot will take over, you will lose your team) in 3 weeks after your last log in. So, if you log on your account today but do not log in for the next 3 weeks, its gone.
It might be 4 weeks, I'm not sure.
If you forget to or just dont set up your lineup for the next game, the default lineup will be set. After setting your lineup lets say for the next game, you can tick the box "Default Lineup " and then that same lineup will be default.