I have Adsense on two websites and have done for about 5 years.,
Site 1 is still active and is increasingly getting more visitors over that time. It earns most of the money.
Site 2 is now pretty much defunct, but has some archival use, so I keep it live and have left Adsense on there. I haven't updated it for a few months, although I very occasionally add something new.
At one point site 2 was doing very well in the SERPs and earned a decent amount. In fact, even though it had less visitors than site 1, users seemed to click more.
However, over the past year or two, it lost a couple of major inbound links and no longer does as well in the SERPs. Probably quite rightly, but anyway... It probably only accounts for a small percentage of income now, but it's still money ;)
My question is, for 'Smartpricing' or other reasons, should I keep this site live, or could it be harming the earnings of the main site? Adsense appears to work across user accounts, rather than individual domains?