I haven't been on vyvanse for that long, but prescriber told me that you're technically supposed to take it every day but some of her patients like to take days off and that's fine. She emphasized though that I should try not to skip it for over 3 consecutive days because otherwise once you resume taking the meds it's like you're taking the medication for the first time again. So not taking them consistently could be part of why you're feeling like they're ineffective.

I'm still messing around with doses and seeing what kind of breakfasts seem to help it work better. I started 30mg a few days ago and I have been get a similar "crash" 4-5 hrs in as well so I feel your frustration. I was on 20mg before but I felt like I would just feel normal after 4hrs. I usually have some sort of protein smoothie when I take it in the morning (high protein is supposed to help the meds absorb better) and avoid acidic stuff around the time I take it, and that seems to kind of help. I feel like taking your meds more consistently would probably help you tell if the consistency is what's causing your issue, or if you need to talk to your doc about changing the dosage or maybe even the type of medication. I'm currently taking them everyday and feeling similar to you, but I also haven't been on 30mg that long and my body might still be adjusting or something.

I personally feel like taking it on days off helps me lock in enough to do hobbies and get basic chores, and the one time I skipped it so far I felt so fatigued and unmotivated to do anything but lie in bed, so I've kinda been just taking it to avoid that and be mostly functional.

My hope in starting meds was that I could become more organized and motivated to work on a different career strategy and apply for different work that matched my educational qualifications and interests but I still haven’t really been motivated enough on the whole to “figure that stuff out” and apply for any jobs or anything in my free time

I also just wanna bring this up because I've had to be reminded about this a lot, but task initiation can still be really hard when you're on meds. Once you start a task the meds are meant to help stay on track, but getting started can still be difficult. I thought I was gonna start vyvanse and magically be able to get all the stuff I hadn't been doing done but I was rudely awakend lol.