Epson 1520 problem

I have an Epson 1520 printer. Is it necessary to leave the print cartridge in the printer when it is not being used for an extended time?

Yes. Epson user manuals warn not to remove ink cartridges except to immediately replace them with new ones. Where an Epson printer is presented for warranty repairs, and no ink cartridge is installed at all, then cost of repair of print head related problems, including replacement ink, are to the customers' expense.