Tim,
I don't know what your performance level is but I think your question really comes down to what you consider ideal weight. As I approached my 40th birthday I was overweight and out of shape and started working hard on getting back into shape. I'll spare you the details but I reached a point where I lost 50 pounds and was at a weight I considered ideal, I got just below 10% body fat, was running faster than I had at any point in my life, was lifting weights regularly at higher amounts than I had previously and all of my key health indicators (BP, Pulse, etc.) were all great.
The same is true today at 44 (I'm a little slower running but much stronger in terms of weight lifting) and I consider myself at an ideal weight (158-160 pounds and I am 5'10) for an active middle aged dad. My body fat is now closer to 11-12% and I still love to run and depending on the situation with COVID I hope to compete in about 15 to 20 races this year. I probably won't win any but I'm likely to be competitive for my age group. I run daily and lift weights 3-4 times a week but training while important is not the primary focus of my life my family is and I do it more for stress relief and to stay healthy than for any competitive advantage.
I can say that maintaining my weight with an active lifecycle is easier than losing weight. To lose weight one must consume fewer calories than they burn, to maintain you just need to equalize. For me the difference is a few glasses of wine and beer a week as well as not worrying if I have dessert or a pizza instead of salad etc. I would consider it my "natural" healthy weight and one that would probably be normal had I lived 50, 100 or even 200 years ago.
However, I am not an ideal weight for competitive running. I could still lose another 15 pounds and still have what is considered a healthy BMI and that would likely make me faster. some on this board might argue that I should lose 20 pounds but personally I think that would degrade my performance but that is a matter of opinion and debate.
So I think it comes down to what you feel is ideal weight. Is it one where you like the way you look, have lots of energy, have healthy blood pressure, cholesterol and other things, are competitive to the degree you want to be or does a ideal weight mean that you have reached the lowest weight at which medicine still considers you healthy and at which the experts say will help you run the fastest in the distance that you race. The latter is much harder to maintain b/c for many people it is not a "natural" weight to be at it is achieved only through high training rates and limiting caloric intake.
FWIW when I ran track in HS I would frequently gain 10-15 pounds over the fall and winter and come into March weighing 155 pounds and by the time late April rolled around would be at 140-142 simply b/c I was training much harder and competing. As others have stated it probably isn't healthy or reasonable to maintain a race weight year round but again it depends on what your goal is. I am fine racing at a weight that isn't as low as it could be b/c I'm not trying to make a team, win a specific event, or set a record. When I compete I do so for fun.