How did you know if the pay rise was fair if you hadn't researched what other roles are paying though?
Honestly if I a team member come to me around salary, we pay them what they are asking for, then 5-6 months later with all else being equal they rock up and say "yeah I want 3-4% extra" I would be losing confidence in them unless they were presenting a strong case for it (perhaps someone left and their role has evolved to cover more than it did at the start of the year). Off-cycle pay reviews can be a massive admin headache and in some organisations you have to provide justification to multiple levels of management and HR. I was more than happy to 'go in to bat' for my team where I felt they deserved and raise, and did this on more than one occasion (sometimes pro-actively before they raised any issues). But I wouldn't be happy having the same conversation again so quickly and would start to wonder why this person hadn't looked to agree the number they wanted when we were in negotiation earlier in the year. I could see them becoming a 'problem child' that will be like Oliver Twist and keep coming back with their begging bowl. If nothing else it puts the manager in an awkward situation, either they are rejecting the request and annoying the employee, or they are coming cap in hand to the Director again on the same subject making themselves look silly. To put this in context, in my prior role such pay rises had to be approved by the CIO. You bring pay adjustments to the CIO in batches for approval across the whole division, you don't just randomly say on a piecemeal 1-by-1 basis every few weeks "yeah Joe Bloggs in team X, you've never met the guy, no not Jim Bloggs I asked you about last week... yeah that's right the one we gave a rise to in Jan.. yeah... anyway we want to give him another rise. "
