I've been known to use 3 different machines on the same project- one machine I take to classes- it's small & lightweight, one machine lives at work- I can set it up & use it during 'down time'; and then the machine I have set up at home- one's a Singer, one's a Janome & ones a Viking...I always make sure I have the same seam allowance- I've often used different threads in each machine- without problem. the reason behind sticking to one is of course consistency- if you are able to achieve the same consistent seam with different machines you shouldn't have a problem.