A purchase price allocation is usually mechanical. Identify the intangibles, value them, allocate the residual to goodwill. It stops being mechanical in four situations, and it is worth knowing which one you are in before the timetable is set.
An earn-out turns a one-off exercise into a recurring one. It has to be fair-valued at acquisition and remeasured every period after, and the assumptions have to be defensible each time.
The most commonly recognised intangible depends on attrition data that many private targets simply do not keep. The workaround is not to guess — it is to say what you used instead, and why.
Negative goodwill is treated as a red flag by auditors, and reasonably so. It usually means something in the allocation is wrong. Occasionally it is real, and then it requires a reassessment you should document before anyone asks.
Two acquisitions in one period is not twice the work — it is more, because the comparison between them invites questions neither would face alone. Consistency of method matters more than the individual answers.
If none of these apply, a PPA is a fortnight. If one does, plan for longer and start earlier.