I started doing more deliberate meditation practice last summer and logging my sittings with the Android Meditation Helper app. I've been doing samatha jhana concentration meditation as described in Daniel Ingram's book. I've started hitting subjective states that resemble the description of the first jhana in the last few days. I've noticed that my concentration during the meditation has been consistently better than it used to be for a month or so. Before that, I had intermittent episodes of heightened concentration where I stopped having distracting thoughts, while most meditation sessions were a constant struggle to remember the meditation focus instead of having my mind wander.

My ideal meditation practice for a day is an hour in the morning and an hour in the evening, but I haven't managed that very often. The stats show 168 days since I started logging meditation with the app. From these, 34 days had zero meditation logged, the median total daily meditation was 45 minutes and the mean total daily meditation was 48 minutes.

So that's a tentative verification that a somewhat consistent meditation practice really can help achieve otherwise unusual mental states, with benchmarks for noticeable intense concentration states starting to show up around a month into the practice and preliminary jhana states of full-body feeling of pleasure around six months in.

EDIT: I've since read a more detailed article on the jhana states. The experiences I had resemble the pitisukha precursor states described in the article, not the actual jhana states described in that article.