Truthfully except for the busiest days you can get USS done in a day. Especially if you spring for Express.
I love USS, but Singapore has so much to offer - i'd really recommend trying to knock the park off in a day so you can do other things on the other days. There is no shortage of things to do!
We've just booked our third trip since 2022 to Singapore, this time round we've allowed more time to explore Changi (we're still discovering new things at that bloody airport) and we're planning on a stay at the Banyan Tree lodge at Mandai.
I'm not even sure if we will go to Universal this time around.