Buying and admiring your newest 'investment' is only the beginning. To increase, or at least maintain its original value, you have to go through the bare minimum.
Get a well-cushioned display case with a see-through cover, preferably with good quality glass or plexiglass, set in wood. True, the pens themselves come in attractive boxes, but to get the most out of their presence, this is one addition you cannot do without.
ALWAYS GET GOOD INK
While writing is almost on the way out from our lives, never compromise on getting quality ink for your fountain pens. Ink from renowned brands like Pilot, Pelikan or Mont Blanc do not form clumps in the inner tube or the nib, and are availble at the very store you bought your pens from. If you opt for ink cartridges, again, settle for reputable brands only. In case you want to experiment on what works well, a good connoisseur tip is to keep a cheap fountain pen for such testing purposes only.
THE NIB OF ALL THINGS
The heart of the writing utensil is the nib, which also happens to be the most delicate part of the fountain pen. Caring for the nib varies from brand to brand, even within the same brand. So pay attention to the make and mark. The nib also works best if only one person uses it, as writing pressure varies greatly from person to person.
THE FULL PEN WORKOUT
A fountain pen needs to be cleaned out at least three to two times a year, whether you are using it or not. Most brands these days give out extensive caring instructions with detailed diagrams of the innards, so pay close attention to these before dismantling your pen.
If you happen to have the type which uses ink reservoirs made out of rubber, take extreme care so that it does not rupture.
While the caring does seem tedious, remember, any fine mechanical instrument has its upkeep. You cannot imagine a well-kept classic Alfa Romeo without regular oil change, to say the least. It goes the same for your branded fountain pen, so happy collecting and caring.