You might ask if they retest in six months if you're concerned.
I second that suggestion: six months.
Let's say you were to wait one year and the result came back, uh, 5.93. Wouldn't it be helpful to know whether at six months it was > or < that level, so you could tell whether the PSA was continuing to bounce or was now steadily trending up? It's a cheap, easy test. That would be my call.
BTW, be sure to keep using the same lab and the same protocol. I noticed some of your prior PSA results were carried out to one decimal place, others to two.
Age 60 at dx 7/2017 biopsy G8 (4+4), 5/13 cores
RARP 8/2017 (Patel), pT3a N0 M0, 30% tumor; EPE+, SV-
PSA 1/2016, 2.9; 4/2017, 7.2; 9/2017 (post-RARP), 0.13; 10/2017, <0.05, 1/9/2018, 0.09, 2/23/2018, 0.08.
Eligard started 3/2/2018. SRT 72Gy, 40 fractions, finished 5/8/2018
PSA 8/2018, <0.02
Caution: I’m not an MD and don’t know what I’m talking about