All Epson printers are designed to print relatively clog-free at a minimum relative humidity of 35%. That is actually a difficult number to achieve without using humidifiers. But, it is essential to keeping the nozzles from skipping around and imitating "clogs". This may be your over-riding issue with clogging. So purchase a hygrometer and measure and keep the air minimum 35%. Strive for 40-45%.
We keep our studio at 35% and have trouble free printers using ConeColor and Piezography. When we dip into the 20% range we have skipping nozzles.
The Epson 4900, 7900, 9900 printers are prone to permanently clogged print heads often in less than a year. The internet is filled with unhappy owners of these machines and head replacements have been numerous.
The 7890/9890 does not suffer to the same degree.
The main opinion is that the new thin film print heads have ink chambers that are about half as narrow as should be. The new Epson print heads which they designed after these have chambers that are twice as thick and these are apparently running more trouble free in their $100,000 label printers. Unfortunately they do not appear destined for new model LF photo printers. So, the 4900, 7900, 9900 while great printers, should probably only be purchased with extended warranties.
Having said all that - Epson printers should be printed on frequently. Once every 2-3 weeks invites pigment settling issues.
If I has a choice, I would purchase a refurnished warrantied 7890 over a 4900 or 7900. But I would not let is sit for three weeks unattended.
Hope this helps.