Depending on how many you would buy hypothetically if they became available like that, you may want to consider getting the Ultimate + that has all the explanations. (With the exception of some LRs from PTS 1-15? I think)
@"Alex Divine" That's actually the reason I upgraded to Ultimate+, to get access to the LR from the earlier tests. The explanations for LR are from PT's 17 onwards, and RC explanations are from PT's 1 onwards.