Should I bring this up to my potential future employers? And when?
During the interview stage, or when I finally get the offer, or when
I'm actually in the job?
You haven't indicated if these "future employers" will be for contract positions, or permanent positions. I'll touch on both of them, and I think the same thoughts apply to each in differing degrees.
Whenever I hire a contractor, I always ask when interviewing if they have any planned time off during the contract. That time away may or may not preclude my hiring them - depending on the length of the contract, and the length and timing of the vacation. If I have a 2-year contract, a few weeks away isn't likely to cause any problems. If I have a 3-month contract, a few weeks right in the middle of crunch time likely means that this candidate isn't a good fit.
When I hire a permanent employee, I also ask about planned time away. A few weeks here isn't likely to matter since I can always advance some vacation time that isn't yet accrued. Many weeks or months may make a difference though. Sometimes it means delaying the start date until after the vacation time is consumed, on rare occasions it means that the candidate isn't a good fit.
Either way, if the interviewer doesn't ask, you should bring up your planned time off at some point during the interview. My suggestion is to wait until you are at the acceptance point - the point where you and the company have determined that you are a good fit, you have agreed on a rate, and are perhaps just exploring details or negotiating benefits.
You need to decide ahead of time how flexible you want to be. Would you consider cancelling one of your planned vacations?
Ten weeks of time off is a lot in my part of the world. Currently my company offers two weeks of paid vacation to new hires. To accommodate someone with a need for eight additional weeks off is difficult. It can be done for the right person, but that person would have to be exceptional. And let's be honest here - by definition, very few people are exceptional.
If you are planning on contracting, you can certainly work around your vacations. Plan on taking gigs that don't clash with your planned time off. It will take you longer to find such contracts, but that could help balance your professional reputation with your need for free time.
If instead you are planning to seek a permanent position, you might want to make sure your vacation bookings are all refundable. That way, you won't need to turn down a dream job just because you have already booked an expensive vacation and can't get your money back.
Try to be as flexible in your planning as you can, and when you can't be flexible, be very open and honest with your potential employer. You don't want to surprise a new boss with "Oh, I didn't mention it during the interview, but I need these 10 weeks off." That's a poor way to start off any new job, and could lead to a major conflict if the request for time off is denied.
Maybe you really don't need a job right away? In that case, it might be easier to get these vacations behind you before concentrating all your energies on finding the right job for you.