The amount of carbonation should not change over time, unless the cap isn't sealed. You lose some small amount of carbonation from keg to bottle, but once capped and allowed to settle (CO2 in beer and headspace equilibrates), the carbonation should stay constant. I try to fill my bottles from keg until they overflow and there is almost no headspace. I also slightly overcarbonate my kegs so I can fill bottles, lose a little carbonation, and still have good carb in capped bottles.
This has also been my experience with bottling from a keg using my beer gun.
My bottles are as carbed as my keg was and come out perfect. Plus you dont get the sediment in the bottom of the bottles like you do with bottle conditioning. It looks like store bought beer which is nice when you are handing out beer to folks who are not used to drinking homebrew. I have alot of beer drinking friends I give my beer to ask me how I have clean bottled homebrew beer as alot of them are used to drinking bottle conditioned homebrew. I tell them the beer gnomes are my friend and sweep the sediment out of my beer. lol
Back when I was bottle conditioning, I was having to explain to the non-homebrew crowd I gave my beer to what that "gunk" was on the bottle of my bottles and it was a turnoff for a few of those folks. Bottling from the keg eliminated that.
Another few really pros of kegging beer is:
- You can also "jump" the beer from one keg to another with almost zero oxidation exposure. I have done this to move beer from one keg to another to clean the beer up clarification wise or if I am taking a keg to a party and dont want to worry about stirring up any sediment during the ride over to the party.
- You dont have to bottle the beer until you are ready to bottle it (or just tap and drink from right from the keg if you can drop it into a cooler and pack it with ice to chill it or put the keg into a fridge) and its ready to drink when it hits the bottle.
- You can "sample" the beer as its carbing up without having to crack an entire bottle to get an idea of where the beer is carbing wise.
- Its just easier all the way around maintenance wise..when the keg kicks, rinse it out, sanitize it, pressurize it and store it for the next batch.
Cons:
- Its more expensive. Kegs prices are on the rise and will continue to rise as long as the craft beer craze continues to ramp up. Plus you are having to keep Co2 on hand, get a pressure gauge, hoses, etc. It adds up. Get a "reconditioned keg starter kit" from your LBHS with used ball lock cornies if possible. The "reconditioned keg" kits are usually the cheapest way to get into kegging as it will come with what you need to get started at minimum. Get 2 kegs to start..Trust me..if you get one, you will be needing another before you know it. If you are brewing 10 gallon batches, 2 kegs are required to keg the whole batch.
- If you want to serve from the keg cold, it does require a fridge/keezer/kegerator to do (to keep the keg cold). Again, not required, but is a nice to have.
The only regret I have on moving to kegging beer is that I did not do it sooner. Its the best of both worlds and really opens your options up packaging-wise and serving-wise with your beer. As for your original problem with off tastes, I 100% think kegging reduces the chance of getting those off-tastes popping up in your beer when bottle conditioning. I know it has in my experience.
Good luck and keep us posted!