.908 for 3 1/2 hrs is not typically realistic. You should be losing ~5% per hour from what I've read.
300 TSS is almost always a "baked" day. I would say especially on a CTL of less than 100, make up of the ride not withstanding.
That being said, two races on Saturday, the bike rides to/from plus warm up/cool downs were 260 TSS for me and I raced twice the next day twice for another 250 TSS.
I almost always know when a ride of that magnitude is going to happen and it's on the last day of the training week - rarely with a ride the following day. The risk of over-training is just too great.
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