There isn't anything wrong with reheating a solder joint
if nothing immediately attached or near it will be damaged from heat; because it may a decent amount of heat. I use Kester 44 solder, and it is lenient for this practice.
The important thing to do when soldering to begin with is keep a careful watch for the solder to cling to both surfaces. If it isn't, we call it a cold solder joint; because one piece did not heat enough. In fact blobs are often a sign that the solder did not run onto the piece you are connecting. It takes an incredible amount of solder to look like a blob without a cold joint, most of the time.
Even if you don't tin wire, you can heat wire up before trying to attach it to anything. The idea isn't that you have to heat it a LOT, but the solder is harder to see running onto it than it is a terminal/rca/etc, so it is a little reassurance. Plus typically the wire will dissipate some heat on the run to the starting location, and what you solder to may be more heat sensitive.
SMD's are tricky stuff. You can blob solder on, and suck it up, to get attachments. But you want to quickly touch each pin that doesn't have a CLEAR non-cold joint. If it looks like a mini blob at all, it mostly likely need to be heated in order to run a non-cold attachment to both pad and pin. The pins usually will take on a decent amount of solder (it'll wrap all the way around them). Careful, careful, careful, SMD parts don't like heat. Reduce the working time as much as possible or come back to it if you had trouble. Personally when I want to remove a bad SMD chip, I cut the legs with a razor blade and flick them off the pads with a soldering iron (wish I had a needle nose soldering iron). It is way less of a headache and only take a couple moments.
The future might be SMD's, but my future only involves a hot air soldering station or the rare hole mount kit
