I think how mB12 affects you changes over time, depending upon the status of other things.
I have read that if you're mB12 depleted the half-life can be only hours, but I haven't researched to verify that. I've also read that it only takes 3 days to become completely depleted of it, but I haven't verified that, either.
Adenosylcoblamin (a different type of B12) is different. Your body needs that, too, but it is stored in the mitochondria. If you have a good supply of adB12 it takes several months to become completely deficient in that form of B12.
IMO when you should take mB12 nd how it affects you depends upon the state of your health, your snps, your stress level, alcohol intake, and other things. When you should take it to get the best results may not stay static over time.
I hesitate to say something like "the half-life of mB12 changes over time", because scientifically speaking I don't think the half-life of any substance can change. But your body can process it more efficiently or less efficiently over time, thus changing the uptake of the mB12 into your cells, as well as the level of excretion, etc. So it *seems* like the half life may change.
For example, after I got my first mB12 injection my body seemed to crave big doses of it for months. It was like, "Eureka!" Loved it. I was going as high as 5mg/day injectable, plus 20 mg/day (or sometimes more) sublingual, spread throughout the day. I injected in the morning then took sublinguals at fairly regular intervals spaced throughout the day. Sleep was good, and for a while it seemed that mB12 was actually making me sleepy during the day after I took it. But that went away.
I had also worked my way up to commensurate amounts of folate.
But now, after months of large doses, I seem to have gotten myself "topped out "with mB12. It's like my reservoir is now full. I don't need as much of it daily, and in fact large doses per day now adversely affect my sleep. I've taken it way down. This seems to happen to other people, too. I find I'm doing much better on much smaller amounts of B12. I typically take a 1mg injection in the morning, with maybe a 5mg sublingual mid-day (but usually not). That's all.
If I was you I would experiment with different doses of mB12, maybe adding some folate. Recommend to try some adenosylcobalamin as well, but definitely only take that in the morning. It can be stimulating. The same with LCF. If you try it, do it in the morning. Also, with LCF, start with small doses (like half a 500mg capsule) until you see what works for you.
Also recommend not to try SAM-e, TMG, or any other methyl donors until you see how you do on those foundational supplements mentioned above.
I can't emphasize strongly enough the need to be able to listen to your body for feedback about what works and what doesn't, and also to do a lot of back-reading on this forum. I could not have accomplished what I have so far if I had not done all the back reading I've done, especially when I first got here. You know your own body and your symptoms better than anyone, so just getting advice from other people may not help you as much as doing your own homework. If you do your own research you find little nuggets of information here and there that become really crucial to your recovery, but the nuggets address small things you wouldn't think to mention to other people, maybe even your doctor. I hope that makes sense..