That works fine when your remote is only in the range of one but not the other. But once you're in both, that'll cause odd problems. The reason is, X-10 has virtually no collision avoidance. The smaller transcievers that came with Firecrackers have none at all. So if both transceivers see that signal and send it at the same time, and your phases aren't completely separated, what'll happen is you'll get two X-10 signals overlapping and changing into some garbled signal that could do almost anything -- except what it's supposed to do.
Now, you might never run into that, if you've only got two transcievers, they're on separate phases, and your bridging is completely severed, or if you are never in range of both at once. But if you do run into it, it'll just look like inexplicable signals turning off unrelated devices or signals just being outright ignored, both of which might lead you to the wrong conclusion if you don't know about this effect. So keep it in mind in case it comes back to bite you someday.