Does B2 visa sponsor has to be in USA at the time of future visits by visitor

[hmbj]

I am currently in US and planning to sponsor my parents for B2 visa. In future, if I am not in US, still they can visit US as long as their visa is valid? If not, what can be done at the time of visits? At that time can someone else show that he/she will sponsor the visits? Note- Reason I am asking this is usually 10 years visa is given and I being on H visa might not be in US that long.

Thanks in advance.

[immihelp]

That's ok.