Depending on the product, maybe forever.
I have some bad news for you: viruses and hackers don't care about your support contracts and the delays they cause.
Actually, I tell a lie: the hackers love them.
a) It's very rare to patch things manually
b) It's very rare to develop patches yourself (for 3rd party software)
I'm sure some companies out there with many decades old deployments have to do stupid shit like that, but it's hardly the standard.
If it’s some important piece of software you also can’t stop or the business stops - well, you and everyone else is just going to take it in the pants.
Many enterprises are in exactly this bind. And support contracts only get you so far.
Many people don’t even realize how long it can take to get a real issue fixed even with a super sweet support contract. For instance, I once was a wet behind the ears Oracle DBA, and when creating a schema i dumbly used a feature in the documentation without checking to see how long it had been released. Unfortunately, it had been released about 6 months before, as I found out later.
It took 6 months for them to figure out that it was the cause of our sporadic ORA600 errors (aka core dumps), by which point we’d already migrated to MySQL for many of the workloads because the database was having at best 95% reliability because of it.
Once we migrated the table off with the feature, somehow our problems ceased, but that was still well before they told us what was going on.
I’d guess people running commercial non source available binaries in production. And outside startups and unicorns, that’s almost everybody.
How do you find the dependancy tree for your on prem Oracle db, or your self hosted Atlassion stuff, or your non cloud ServiceNow or PeopleSoft stuff, or your Huawei network management stuff, or or or…
And what can you do for any of your cloud hosted saas stuff, beyond telling legal “I dunno, their website hasn’t said whether they’re vulnerable to exploit de jour yet”?