I think you are going to get a lot of answers here, everyone takes a different tack on workouts, indoor vs. open water training, etc. I swam distance, and certainly did swim 500 yd, 100 yd, mile, etc straight on occasion. That said, it is pretty boring, and not a great way to build strength, just endurance.
More typical would be 5 300’s, or 10 100’s. Some build speed, some build pace, some just make you cry like the 3 3,000’s day.
In your workouts, you should be splitting these up so you are addressing different strengths, and also it should be part of a total plan building towards your racing goals.
If you are just getting swims in whenever you can, here is a set I like that isn’t too boring, and easy to do without a clock. Called a ladder, or loco. What you are doing is building up to a distance, then dropping back down. Have a set rest inbetween sets, you can make it harder by reducing the rest. Start with something that you find difficult, swim till you can make it relatively easily, then drop it. For 1,500, it would look something like this (actually 1,550):
on :10 seconds rest:
25
50
100
200
400
400
200
100
50
25
Lastly, it sounds like you could use a structured workout. If you PM me, I can email you a free one that has swim workouts tailored for Oly distance