Random answers without quoting:
The less expensive pens from Penn State are typically Cross-style refill ballpoint. A slightly more expensive pen style uses a Parker-style ballpoint. The most expensive pens are roller balls and fountain pens.
For the purposes of this discussion, I'm assuming you're using Cross-style kits or Parker-style kits. I have personally had on my desk and on my kids' desk Cross-style pens, unused, for > 2 yrs. When attempting to write, they write pretty much immediately. The Taiwanese-made Cross-style refills in the Penn State kits are pretty good. I don't have age data for Parker-style kits yet. But I conclude that these Taiwanese Cross-style refills are far, far better than most or all generic office store pens.
I've assembled Cross-style kits which are more than 3 yrs old (don't ask). The ink flows pretty much immediately. I keep most of my kits in my garage (hits > 90F in the summer). I have a few more expensive roller ball kits in the house; working on donations for benefits, retirement presents, and graduation presents.
Some of the Penn State kits now come with a rubber or plastic "nib protector" on the end of the ball point. This is an attempt at giving the pen a longer shelf life. After you assemble the pen, but before you press in the transmission too far, put the refill in, and test the transmission. To do this, you must generally remove the nib protecting piece of rubber or plastic. (You can generally put it on again after, but I wouldn't bother, personally).
One hint (DAMHIKT): Twist the transmission to fully retracted (for Cross-style pens) before pressing. Insert pen refill, screw it in, then, check for proper transmission depth. If you press the transmission in the extended position, there is a possibility that you could cause the transmission to buckle.
Regarding styles: Most of the less expensive kits are cap-less pens; twist to operate. The more expensive kit styles are capped pens.
The easiest kits to make are the single-tube kits (which, for the most part, use a Parker-style refill). The least expensive kits are the slimline and relatives.
Anecdotally, the PSI "funline" are of lower quality; transmissions don't work as well; platings wear off; etc. This is hearsay, and I don't have personal experience there.
If you're attached to either the wood or the pen kit, you're less likely to learn. Practice on cheap pine, etc.
Mesquite makes for beautiful pens, especially if you find some transitions from sapwood to heartwood in the blank.
Of the gifts that I have made: I know 3 users personally (colleagues at work) who use the pens daily. One more co-worker doesn't; it's a display piece.
Check out my gallery of turnings on Picasa at
https://picasaweb.google.com/hy.d.tran/Pens#