Hey everybody. It's been awhile since I was on here.

Anyway, I frequently use a local system of trails and bike paths for getting around on my bike. My main bike for the last 3 years has been one of those shunned "____-Mart" bikes. It's a Magna "Great Divide".

Before you all go urging me to upgrade asap, I have two points to make:
Firstly, my budget is extremely constrained. Although it is a major hobby of mine, I primarily bike for utility and just getting around cheaply.
Which brings me to my second point: This bike was the cheapest one on the store when I bought it a few years ago. I have had more expensive mountain bikes in the past, going up to about the $200 range. (Admittedly from a dept. store. It was a gift.)This one was $60 on clearance, and it's outlasted anything else I've ridden by a huge margin. (I'm definitely not nice to my bikes) I don't know if it's a fluke, but clearly something was done right the day I bought it. It rides nice, (as far as my standards go) and it has always been extremely reliable. I ride this bike alot.

That said, I am interested in upgrading my bike in the future if I can afford it. My strategy so far has been to replace parts "as needed" with superior quality replacements. Eventually, I'll have a better bike. (Right?)

*Note: So far, I've hardly had to replace anything, but I might decide to do so without waiting for stuff to break, depending on the responses I get.

The problem there is, the frame is still low-quality and (presumably) weak, even after all the components have been replaced. Is it worth it to take this approach? Perhaps if I were to replace the frame itself at some point with a good one, moving the components, wheels, etc over to the new one. Would there be any parts compatibility problems with doing this? (Assuming I get a typical frame for a $500 mountain bike)

Will this get me a decent bike in the end? I really can't see myself just buying a whole MTB at once in the $500-ish range, but I can probably do it a little bit at a time. (We're talking over a duration of maybe 3 years, here) Otherwise, I'll probably just keep riding the bike the way it is for a long time.

Frankly, the answer I'm hoping for is that I can upgrade it a little bit at a time and eventually get a better frame as well, and that this will make a good bike. (Or would it make sense to replace the frame first?)