If you're a beginner I think it's really important to pick a tek and stick with it as exactly as you can. After you have a successful extraction or two you can start refining your technique or moving on to other teks.
If you've decided on doing an A/B extract,
Vovin's tek recommends 45 minutes. Be very careful about overheating and use a hot water bath as described in the tek.
All the A/B teks are here:
https://wiki.dmt-nexus.me/Category:Acid/BaseGood luck!
peace
Phaedis