I now agree with virgin (changed my mind) it is best to keep an old email address used for about 20 years anyway even though it gets lots of spam emails. After 4 years I am still getting some valid email from accounts I had forgot or ceased using for a while but needed sorting. Also these days it is best to keep hold of all email accounts old and new to be in control and prevent recycling or hacking of the email by doing regular activity. I have noted some ntlworld.com and virginmedia and virginmediabusiness.co.uk.com email accounts are used by spammers now so it is wise to keep control of the primary email even if it is a spare email or no longer used due to spam issues etc.
perhaps virgin are wise in that regard and not using it for 150 days would result in loss of access/monitoring/control
I just yesterday had to deal with an important account not used since 2018, so good job I have maintained primary email.
genuine emails can suddenly appear form old accounts from years ago, so glad I still maintain this email now.
always wise to check authenticity of emails using "view source" but contact the company directly rather than click on any link go via their official web page
log in and ensure address is https. ( this avoids phishing)
if spam is troublesome it can be dealt with using blacklist and filters see "spam and blacklist posting" (using regex filtering)
check password works regularly and change often is what I do. I also use secondary virginmedia.com email accounts.
Virgin let a lot of spam through and should use Bayesian filters which are readily available, some email provided stop all spam.