Bit of an urban myth you fell prey to. Yes, ther are some ropes that are a pain when it comes to splicing both ends. However, generally speaking with most ropes in use today it is not a huge issue if done well. Splice the first end, equalize the cover and core. I like to do this by climbing on the line for a few days in nice weather. Then splice the opposite end. Even in situations where my equalization process was not perfect, the minor bunching up would dissapate with use as there is plenty of rope in a 150’ or 200’ line to absorb it. The only time that an less than stellar double splice job would cause issues was if I ran the line the whole way to the end from a single anchor. I never did that very often MRS.
Stitched splices make the whole discussion above moot.
As for your rope, splicing used rope is very difficult even after a few weeks of use. Perhaps a stitched splice now that the rope is aged.
Probably best to just order a double end hand or stitched splice when it is time for a new rope.
Tony