I think Epsons are the exception - they have heads that are fitted for life. All that is changed when you fit new inktanks is indeed a tank with ink in. With HP and Canon printers the replacement ink cart tends to come complete with a new head. Refilling these too many times can lead to problems. The advantage of this is that if you get a bad blockage in one of the nozzles on an epson you tend to be stuffed - on a HP or canon a new cart sorts it. Not sure on lexmarks - we don't have any of those (I suspect they are like the HPs).
Of course, this raises the question of why Epson carts are not a lot cheaper than HP or canon if they are so simple...
Darren