Jen, just relax...don't try to overthink the whole thing right now. Most people, when they start, have a hard time just keeping a few colonies alive, muchless have to deal with to many bees. The whole re-Queening thing will make more sense to you in a year or so. I, myself, never re-Queen unless I want a "new" type of bee in my yard. I too live in Texas and I can not say that I have ever had to deal with Africanized bees. Yes, I know they are here but thus far...no problem.
Your bees will take care of the Queen issue on thier own- they have been doing it forever. The only time they can't "fix" the queen thing is if, say, you squashed your queen in the middle of winter while you were inpecting your hive. Assuming the bees would make a new queen(which is what they would normaly do) once she hatches, there would not be any drones to mate with at that time of year.
Like I say, just relax, you are not going to be inundated with bees (unless you were super lucky!)...keep learning, like you are, and all the sudden this stuff will all come togeather in your head- somewhere in your second season the proverbial "light bulb" will go off in your head! Everything that you have been learning will fall into place.
As for Queen excluders...again, relax. Sometimes I do, sometimes I don't. I only have them on during a strong flow- during which I have an upper entrance for the bees to go in. Thats another subject though. Once you are used to seeing what brood looks like ect. Queen excluders often make new beekeeprs more comfortable.
Oh yeah, Jen, the population of bees in a hive swells and ebbs through the year...it is not a constant upward spiral of bees. All those supers you put on early in the spring will be off...sometimes even the extra brood box- as you hit winter. Your Queen knows when to slow down (or even stop) laying eggs. All depends on the food available. As winter rolls on, a huge hive can dwindle to near nothing...sigh.... go quite a few like that right now!
The only thing you will need to watch for as far as the re-queening issue goes is if all the sudden your hive turns mean- but this is not just a one time thing. Over the course of weeks. There are times when a hive will just be cranky one day for no good reason (that you can tell). Next day all will be fine. This is normal.
The African thing...a hive that always prior was good natured is ALWAYS rotten now...that is when you would squash a queen and get a new one. I have done this thoough I do not think it was African genetics...just cranky genetics. Either way...you will come to know your hive and will know if something does not feel right.
The nice little circle of life you mention is very possible.
Good luck!