Hi, how many trails do you need for one and a half week of riding? Because everyone is different you know...
In Borovets there were about four main trails in 2016 with different levels of difficulty. Additional there are two dirtroads accessible by lifts and one All Mountain track which is accessible only by bike, meaning you have to ride or push to the top of the trail (approx. 15 minutes with AM bike). There is one more option in the high mountain, but that includes some hike-a-bike (approx. hour and a half of it). I still don't know what the bikepark is planning for 2017 - hopefully there will be some new trails.
In Pamporovo there were 6 official trails accessible by lift in 2016 + 2 unofficial + 1 beginners trail. There are also several trails from Pamporovo to Smolyan, but you will need some transportation back to the resort.
There is also a new bikepark Rila Lakes in Panichishte (above Sapareva banya), which had one main track in 2016, but more are expected.
If you like hardcore, steep and loose trails, there is also lift and DH track in Sopot.
And of course, we have an old lift and DH track just above Sofia.
There are also several other great places to ride downhill (Zlatitsa, Petrich, Osogovo/Kiustendil) which don't have lifts, but probably some shuttles can be arranged by the local clubs.
So yes, I think you can make a pretty good vacation.
How many people are you, where do you come from and how - by cars probably?