Jan,
My suggestion would be to try a charge. A lot cheaper than buying all the products. What I have found with my 4900 is that I need to print all the time or it will clog. Also, if I do a head clean, my test prints get much worse on those heads that had shown some minor dropout. I probably need to clean the capping station, so that the vacuum needed for cleaning will work correctly.
Recently, I picked up the Harvey Head cleaner and I have to say that, so far, my problems have diminished dramatically. I have set it up to run a test print everyday and then once a week I shake the cartridges and run a full sized print( I am a hobbiest). Even with the humidity dropping below 35% and not doing any significant printing for weeks at a time, I have had zero problems, in the two months I have had the Harvey program