Hi!
So you are right about Tracy recommending cluster feeding in the evening after BT, but I think not many mothers do it as settling LO for BT is not that easy:))) so after you finally got baby asleep you are not eager to wake him.
What many mothers do is cluster feeding before BT so let say 4pm, 6pm at 7/7:30 top up or 4pm, 5:15/5:30 and 7:00/7:30. Or if the 3rd nap ends before 4pm you can feed at 3:30,5:30 and 7:30pm. So whatever suits you and your LO. You have to make your own timings. Some LOs are not hungry after 1-1,5h, some could eat every hour from 4pm:). The ideas are to tank him up but also to make enough milk for LO as some/ many mothers find their supply slightly lower in the evening after exhausting day and constant frequent feeding during day.
When to end? Depends on you. Tracy recommends up to 8wo not longer. Mothers from here usually continues slightly longer, for example I was cluster feeding up to around 4mo. I decided to stop as LO was used to take full feeds and if not hungry, didn't liked topup's. So I fed at 3pm, then tried around 5:30/6:00 (LO was not interested in feeding earlier...), but in the end DS was not taking any feed at 7pm as wasn't hungry. So observe your little one and try to choose what's better for you!
HTH