I did a similar route a few months ago, as I flew from Chicago (ORD) to Singapore (SIN) with a stopover in Istanbul (IST). The route ended up being ORD to IST (~10 hours) and then a 9 hour stopover, followed by IST to SIN (~11 hours). 30 total hours, but this was to get my flights within a certain budget for work travel ... and thankfully all in Turkish Air business class

If you're on QSuites the entire time, I think it's fine - I was just on a similarly long route from Sao Paulo (GRU) to Doha to Singapore all in QSuites, and though it was 27-28 total hours of travel, it *flew* by, and I arrived in Singapore feeling very refreshed!