How long do rebuilt engines last?

When I was a child, I remember seeing a Mazda RX-8 and a Honda S2000 back in 2003, falling completely in love with them, promising myself one day I would one. They continued to hold my fascination as my favorite two cars over the years.

Well, obviously 16 years later, I can literally buy both of them if I really wanted too. Here's my question: A lot of the ones I see for sale have well over 100k miles on them. If I had the engine on either one (or both haha) rebuilt, how much mileage should I expect to get out of it? And how long should it last me?

Added (1). Dan: You're the second person who has said that! What is wrong with rotary engines?

Get the Honda, rotary engines are junk, rebuilt or not.

5-10 years

A 'rebuilt' engine is only as good as the rebuilder. There are a lot of shortcuts that can be taken. A well built one will be at least as good as the original. Likely even better as the have been 15 years to improve on weak parts (if any) . Both of these are sports cars. Meant to be driven, but how long they will last depends on how they are driven.
!00,000 miles is not that much for a normally driven car, but most racing engines are rebuilt after a few races.

It may be prejudice, but I would go with the Honda.

A properly rebuilt and maintained engine can last a lifetime. I rebuilt my '66 Mustang engine in 1984. Used top quality parts. I had all the moving parts finely balanced by a performance machine shop. I maintain it regularly. 35 years later, it still runs like a sewing machine, but over the years I've had to literally replace or rebuild everything else too. Transmission, rear end. Suspension, steering box, etc, etc, etc.

The down side of what you're considering is that those are much more complex vehicles and far more expensive to restore and maintain than my old Ford. I've owned many, many cars and will tell you from experience that t would be very worth your while to pay top dollar to buy the lowest miles, best maintained (with full records), best condition vehicle you can find, even if you have to search nationally and then travel to inspect it and buy it.

I'd also steer clear of the RX-8. Nice cars, but they aren't trouble-free and over the long run the maintenance is borderline extreme to keep them in good order. Read the forums.

The RX-8 engine is treated as a consumable item. Depending upon how often it's had oil and filter changes (must NEVER use synthetic nor semi-synthetic oil on those) and whether the previous owner has observed the special rules regarding rotaries about warming up and idling before turning off, then those engines can last about 140,000 miles before a rebuild. More typically they get ignorant owners and workshops and need a rebuild at 70,000 miles.

But rebuilding them is fairly cheap and easy.

The S2000 had the most powerful 4-cylinder, normally aspirated, engine ever made. Almost as powerful as the one my Porsche Boxster 986 had, and that had 6-cylinders and was 2.7 litre capacity instead of 2.0 litres. It's a very strong engine and if correctly looked after can easily exceed 250,000 miles without needing a major overhaul.

Honda S2000 is reliable and holds it's used value exceptionally well. The Mazda RX-8 has a reputation for unreliablity, gas-guzzling, and very low resale values.

Mazda had the rotary engine. It does not last long. Won't pass emission standards either.

Honda engine rebuilt would last another 100K, though you could probably buy a newer crate engine for the car cheaper than a rebuild.

A rebuilt engine should last as long as the original new engine did, or longer when it's cared for the way it should be.

If done correctly and maintenance done regularly 200k or more

Mazda RX-8 Rotary Engine was never "sold", it was only leased to the cars owner. If anything happened to it, the engine had to be returned to the factory.

300,000 miles Plus depends on how you drive