When the characters we wanted were with other companies I would maybe buy a few but they never stuck together quite right, or would break too easily. So I wouldnt buy more, or if i did it was just the character and not the set.
You can buy Lego blocks anywhere in the world, and they click perfectly with Lego blocks purchased anywhere else in the world, and purchased at just about any time in the past or present.
Apart from the tolerances that also illustrates what their competitors rarely get right - Lego tends to opt for pieces that are generic enough to be reusable in as many contexts as possible where a lot of the competitors have sets full of pieces that are unmistakably one specific thing. That lets them not worry so much about the tolerances - if it works in that one context reliably, then it's fine. But the downside is it makes the sets even less flexible.
[1] https://www.reddit.com/r/lego/comments/4uv5tl/why_does_lego_...