Would you want to put the money of a resurface and refret into a MIM neck.... and hope it stays put, or put the same or similar moola into a better neck that _will_ stay put?
That's a reasonable question, but you can look at it the other way too.
Most necks do the bulk of their moving and warping in the first year, and then settle in. There are exceptions, of course, but necks that have serious long-term warpage in their DNA will still do most of it in the first year or two. Rarely does a neck stay stable for some years, then suddenly beginning warping badly. Unless they've been been badly externally abused, like being in a flood.
That's why we Luthiers usually set our neck wood strips aside on a shelf for a year or so before using them. If the strip doesn't do anything crazy in a year, then we're pretty confident that they will behave forever.
In this case, what the OP is describing sounds pretty minor. Dips in two spots doesn't sound to me like serious throw-it-away warpage. It may even be able to be fixed with just a fret leveling. The neck is four years old, and that's how much it moved. The most likely case is that it's now fully settled in and won't move any more. You know its history.
If you buy a new freshly-made neck, it may or may not have settled in. Generally, the higher the cost/quality level, the lower the risk of it warping. But, it's an unknown, what will happen as it ages.
If you buy a 5+ year old neck that's nice and straight as you buy it, that's the least risk. It's unlikely that it will suddenly start warping.
That's the question: Spend $300 fixing a neck of known history, or spend $300 or more on another neck, guessing at the risk.
These are things to consider. I just hate to see guys automatically declare that a bass or a neck is Total Junk That Must Be Thrown Away.
