Where I used to live I could hear the girl across the road practising her saxophone - I wasn't going to create a fuss because I think it is great to devote time to that. Much better than the disturbance from the permanently drunk next door neighbour shrieking with her equally vocal friends, and better than the tv sound from my other next door neighbour (on her 90s and practically deaf). But, when you live in a terrace house, you have to accept that there will be some degree of background noise, don't you?
People who are at school/working need, often, to practise before they leave the house in the morning, and again, after they finish work/homework. Personally, I do also think that after 11 is unreasonable, but before that, and anytime after 7 in the morning is perfectly ok.
Should also point out that I am a music teacher, and encourage my students to set aside practise time before school when they are fresh, and also that I recommend shorter blocks of more frequent practise time as opposed to an hour's session every other day.
I work full time, and teach after work, so am often doing lessons til 8 or 9 (as I also have to sort the children out), and then really need some chill out time, when I can sit and play to wind down from the busy time I have had.
If someone came round at 9pm and asked me to stop playing I would feel very put upon in my own house. That said, I have never had a complaint in 11 years of living in a terraced house. Just moved to a semi and the instruments are on the non-detached side, so hopefully will be even easier now.
OP - if I lived next door to a bunch of 20-somethings, I would be chuffed to bits that the only "disturbance" was the sound of classical piano, as opposed to drunken parties and the like!