These domains have been registered using different registrars and I would like to move them all to the same registrar to make them easier to administer.
I realise that this is probably an overly-simple question for this forum, but how do I find a registrar that I can rely on - i.e. one that isn't going to go bust or give me problems moving domains if I ever want to in the future?
So, you'll never know who will be gone tomorrow, or who might have a change in ownership and change their policies, etc.
You learn how quickly and how well they respond to requests for assistance.
You make a call with a question and see how your call is handled.
You use their system and see how well it works. Is it intuitive? Transparent? How well does it perform bulk operations? What type of reports can it generate? Etc.
You shop price, but at bulk pricing levels, price as a significant differentiator is minimal.
Domain transfers and domain security are very important. What is the registrar's record, reputation and transfer protocol? Will they go to bat for you if there is an issue?
IF you have an issue that isn't handled to your satisfaction how easily can you move up the chain of command to get to someone who sees things differently, who will get things done for you?
The more domains you hold the more you have to explore.
Price is a very small factor. Many registrars make their money on added services.
I deal in percentages, I don't like the "all eggs in one basket" syndrome......with a couple of exceptions.....hosting and registrars!
Find the best and make a commitment in those fields!