I would suggest rather than taking Bulk of test series in one day or two try to pratice few questions every day. i cleared Prelims 2020 with 138 marks and used some Apps one of my fav is Be EggHead Academy Mobile App For UPSC Preparation they provide question subject wise everyday new set of questions and also weekly current affair quiz. give it a try. another bonus it free and the standard of questions are upto UPSC Standards
Taking practice test sessions or test series is helpful to crack the main exam. It helps to know the exam pattern also helps to understand your strong and weak subject and increase time speed. UPSC classes in Nagpur regularly conduct test series sessions so students get prepared for the main exam.
Also, crack test series give confidence for the prelims and main exam.