I've been brewing for about 2.5 years now and have somewhere around 80 batches under my belt.
In my experience, an average gravity (4.5-6.0 ABV), non-wheat ale seems to peak at around 12-14 weeks from brewday, obviously not withstanding hop aroma and other "freshness" factors, just the base beer itself.
I think ideally, something like that amber should really be 2 weeeks in primary, then keg/bottle and really let it sit at room temp for another 4-6 weeks to bulk condition, then a good 3-4 weeks at fridge temps, then serve.
Of course, not many of us have the pipeline to wait that long, and the same ale is certainly about 85% of it's peak after about 4-6 weeks. Not to mention, we all make bad batches and it is just a kick in the balls to wait 12-14 weeks for a batch that doesn't turn out.
Anyway, just my observation. I still am drinking most of my batches 4-6 weeks after brewday myself, but just like everyone else, the last bottle is always the best bottle!