My mom had her kids young- between 19 and 23 (she got married at 18 and was almost 20 when I was born). It is great to be young and done. Unfortunately a lot of us are not on that game plan these days (I had my 1st at 29, 2nd at 30 and will have my 3rd at 33 --currently prego). I plan to be done by 38.
If you do want more kids, consider not spreading them out so once you are done with diapers or sippy cups, sleepless nights, or kids toys, etc. -- you are done. In my opinion, it is easier as they grow up to not be going through the baby thing again when you have a pre-teen or teenager.
If you are financially able to, emotionally stable enough to, I say -- go for it! :) I would like 4 or 5...I figure I will "know" when I am at my stopping point ;) ha!