Two visa waivers for US citizen in 6 months?

My wife and I are US citizens considering visiting Japan as tourists twice in the next 6 months. The first stay would be for 30-60 days in December-January. The second stay would be for 60-90 days in March-May. There would be a 40+ day gap between visits. As US citizens relying on 90 day "short term stay" visa exemptions for both visits would there be any risk of being denied entry for the second visit?

It has been more than 3 years since we've been to Japan. Also, we have proof of income from outside of Japan, but we do not have proof of enough savings for the extended (wealthy) tourist visa.

Unfortunately, most data points I have found on this forum (and elsewhere) are from EU/UK residents. Any insight would be greatly appreciated - thanks!

When it comes to this, there is never 100% guarantee, but as long as you can show (if asked) that you have sufficient funds to travel around that long, it should be OK.

By the way the status is called "temporary visitor" :)

I would think they extremely unlikely for you guys to run into problems. Immigration gets wary when you stay in Japan and then go for a few days to Korea... and come back immediately. Even that way it often works out. But you can�ft do that endlessly.
In your car there are 2-3 months in between. So saying something like you want to experience the different seasons in Japan should be more that sufficient as explanation. If additionally you have your return flight already booked, in all likelihood no problems should be expected.

A few years ago I did 1 month in Japan, then a week or so in Mexico, back to Japan for a day or two, back to Europe and 4 weeks later back to Japan. No questions asked.

Enjoy your trips to Japan!

Should be no problem.

I used to visit for extended periods multiple times a year in the visa waiver programme and never any problems.