Some users claim that the Bovida packs impact the taste (in a negative way) of their buds if left in the jar for long term storage. I have used them for long term, but have not noticed any negative impact.
My answer is yes, you do leave the packs in the jar for long term storage. Yes, they will keep the humidity in the jar at 62% for as long as the packs are soft. Once the packs get hard, they are no longer effective. Since the humidity in a long term sealed jar doesn't change much, after 14 months my packs are still soft. When I open a new jar, I put the used pack in a sealed pint jar marked "used" and use them till they are used up. Yes, I am cheap.
Others, who say no, are not wrong either because if they feel it hurts taste and that would be a 'non-negotiable' reason to not use them.
My test was to use them in some jars and not use them in others to find out. How you decide is a matter of personal preference. I hope this answers your questions.
P.S. Welcome to the site