It takes me 15-20 minutes just to switch my mind from "alert problem solving" mode to meditative state in sync with body - and get my breathing right.

I guess everyone is different, for me the practice was looking for guidance and then finding what works for me - one of the first things I had to let go was rigid time schedules, "THIS IS MY 15 MINUTE WINDOW FOR MEDIATETION LET ME SET AN ALARM SO I CAN GET BACK TO WORK" is not a very constructive attitute to regeneration and healing.

I suspect me saying above "Get results after more than a month" instead of hearing "I need to stick to this for a while" people hear "I will definitly get results in 1 month, here let me mark it on my calander [GET RESULTS HERE]" where it doesn't work like that. Maybe you need more healing than I did, maybe you need less. Maybe breathing is important because of how it intertwines with your exercise schedule (or lack thereof), or maybe you need silence or darkness. Maybe you need music. Maybe you need white noise.

The only common thread is that meditation is a personal journey, so listen to your body, try to avoid any preconcieved notions and expectations of results, timeframes and experiement with a few different things until you find what works for you...

I don't meditate, but I do introspect a lot. I often do so on walks. And I find I must give myself at least 10-15 minutes to even get into that mode, to stop worrying about what's actually happening or about to happen or did happen and to be able to let my mind wander and explore things deeply. So I force myself to continue until I reach the point where I'm no longer trying to convince myself to give it up and go home because there's something else I want to do so badly.

After that point, it's up to my subconscious. I'll stop when I feel like it, when I feel satisfied. That could be anywhere from 10 more minutes to another hour. But the longest part is always the beginning. The second part never feels like time is passing - it's exactly what I want to be doing.

Of course, if I only have 15 minutes, there's no guarantee I'm going to reach a place of satisfaction. I would aim to set aside 30-45 minutes whenever possible. I often see "do X for 1 hour a day" and that's just not realistic for everyone. You can definitely get good results with less time investment. But in general, yes you'll get out of it what you put in. I don't walk every single day and I noticeably suffer for it.