The short, annoying and as so often for meno, answer is: it depends.
It's certainly no guarantee, and if you are having fluctuations on something you change every day, extending that time perhaps intuitively unlikely to help - you might in fact want to make the intervals shorter and try splitting your many pumps between morning and evening - I've never been on gel but think I've read here others do this??
If you had an absorption problem, it would not fluctuate, it would just never go up - I think it's with absorption problems that people are often told to try a different method. If you are right and you are sometimes getting high levels from the HRT (as opposed to from your own fluctuations ... might be hard to know if you are still peri if you've been on HRT for 5 years?), you at least know you can absorb gel so I'm not sure why changing to something you don't know you can absorb would help ... (I'm just thinking aloud, no need to answer!).
I've never done gel but think that's a high dose? If you are still getting symptoms your GP should refer you to a specialist meno clinic - long wait but worth getting in the queue. And if you are able to afford it you could see a private specialist in the meantime?
The only way to know if you're getting fluctuations (as opposed to your level is stable but that level is causing problems, be it too high or too low) is by repeated blood tests ...
It's common for symptoms to return after a while doing well on HRT, as our bodies/endogenous hormones change.
I started on patches, partly because a well-known meno 'specialist' told me they gave the best, steadiest, release over the 4 days the patches are designed to last. Long story short, I ended up with an actual leading meno consultant. He said at my first appointment that it was common to have a drop on day 4 and I should change every 3 days - that is not uncommon, although plenty of people are fine over 3.5 or 4 days.
Even longer story short, that didn't fix my fluctuations, and he then recommended the best step was to go to something I changed every day, to avoid the risk of surge followed by dropoff over longer (even longer story short, turns out I have a very unusual uptake pattern so even changing patches daily, which as you can imagine was a total pain, gave me massive fluctuations - at that point he said no point in trying gel or spray). But to stress again: my uptake issue is so unusual that it was only belatedly worked out by a top meno consultant after a LOT of blood tests - and therefore very 'challenging'.
I'm not a doctor though and I've learned the hard way - this stuff is complicated, high doses of oestr from HRT can cause problems, and it's worth seeing a specialist.
VA mimics UTIs brilliantly and so worth trying local oestr. (If only my GP had known that before putting me through 3 years of antibiotics!)
There are others with a lot more knowledge here so hopefully someone will be along to help!
HTH and good luck xx