So you have myolddomain.com and you are moving to mynewdomain.com, do you need to renew the security certificate for the domain myolddomain.com if you are just going to be redirecting it to mynewdomain.com. The answer is probably yes, not necessarily for search engines but users may get a browser error on the redirect.
John Mueller of Google responded to this question:
Merging 2 sites 301 redirect.
— SEO Raccoon Ireland 🇮🇪 (@SEORaccoon) March 4, 2020
Old site A will be merged to new site B
Do I need to continue to pay for for an SSL Cert for site A?
Would appreciated any help with this. @rustybrick @glenngabe @bill_slawski @MrDannyGoodwin @brodieseo @dr_pete @Marie_Haynes @dannysullivan
He said browsers need it, search engines probably don't but since security certificates are free these days, just do it:
Browsers definitely need the certificate for HTTPS, even if you're just redirecting. Search engines can probably deal with it, but if there's a chance the old URL is shown to users, just keep the certificate live too. You can get certificates for free nowadays.
— 🍌 John 🍌 (@JohnMu) March 4, 2020
For how long should you keep that live? John said for at least two crawls, which can mean more than a year?
We usually recrawl URLs at latest every half year, so a year gives you min 2 rounds, which is a good starting point. Even without certificate, I'd try to keep the domain name for the long run to prevent spammers from picking it up.
— 🍌 John 🍌 (@JohnMu) March 4, 2020
The topic of how long do you keep redirects up is something we covered numerous times. In general, keep them up for at least a year but in practice, keep it up as long as you can.
Forum discussion at Twitter.