First, 1.064 is seriously sweet. For reference, apple juice (non-fermented) is around 1.045-1.055. This means that you intend to have a high alcohol brew that is even sweeter then a kid's juice box haha.
If you want it to finish sweet, aim more for 1.02ish. That is closer to what sweet wines/meads finish at.
Secondly, don't bottle until fermentation is completely finished. This means that you get FG readings consistently the same for at least a week or two. Also, you want to wait until the mead is crystal clear, meaning you can read a newspaper through it if you use a glass carboy.
Now, once it is finished, you have two options. Since this is going to be strong, you will need to age it. One option is to just leave it in the carboy and let it bulk age for a few months (3-6). The other option is to bottle whenever you want after it is finished and let those bottles sit for at least 6 months before opening any.