Captain Kal,
The evidence to support Clark's growing powers over time is still in MOS#1. Clark didn't start flying until he was 17-ish, remember? And he was definitely older than 8 when he looked into the next room and found Ma's purse with his x-ray vision, no?
It's not baseless, and there is evidence to support it. Again, how many football seasons could Clark have participated in in high school? If he won the last 5 games for the team, SOLO, that would still be a minority in the season, and more than enough to only start raising eyebrows then. I appreciate your attention to detail.
Given all that is actually stated during Byrne's run in MOS and elsewhere, Superman does not appreciably lose his stored power for any period less than three days. Nothing in canon supports the baseless speculation that his younger self ever had bouts of losing power in shorter periods. Indeed, Jor-El did state that the yellow star would make Kal-El grow ever more powerful. Speculation only counts if some evidence exists to support it. It fails even more if evidence contradicts it.
I don't believe that it was ever clearly stated that he had bouts of losing his powers per se. I am merely looking at it from the standpoint of what a rechargable battery can do. It stores energy just fine as long as it is plugged in. However, it doesn't store energy nearly as well if you're using it at the same time. Now, if the energy is low to begin with, and you use energy while it's charging, you could run into problems. This on top of the fact that as he gets older, his body should be able to store and process the energy more efficiently (one would think.) Putting this all together should reasonably support what you may claim to be a "baseless speculation."
Furthermore, if you want to take it one step further, the powers would never necessarily disappear per se, but the power levels would fluctuate. I don't think that
THAT is too much of a stretch.....