Every beer you make will be a bit different. Unless you have a very controlled enviornment (controlling mash temps when/if you go AG, fermentation temps, amount of healthy yeast cells, etc.) then there's no real way to get everything to be exactly the same. We can come close, though. Homebrewing is all about waiting, and eventually (when you get a good pipeline going), you won't have a problem with patience.
I usually do a beer every other weekend so that I'm always stocked. Unfortunately, I haven't been able to brew in a few months since my garage is a mess and my rig is in the process of being remodeled. I'm almost out of homebrew other than a 2 sours I have aging and a few bottles of each of my last 8 or 9 batches.
To answer your question though...it's not uncommon to have two beers carbonate differently. Two weeks is what most kits and books say, but that's the bare minimum. 3-4 weeks will give you a better tasting beer since it's been aged a little bit.