How long can I go with an obsolete phone?
Right now, I have a Samsung Galaxy A12 phone, which has done everything I need for quite some time. It was bottom of the barrel in the Samsung lineup, and it quit receiving updates of any kind back in November of 2024. For a cheap phone, I've been pleased with it.
My use case is unusual. I rarely use my phone to go online, but on occasion, I am forced to do so. Most of the time I use it to make calls, or send and receive texts. SMS is fine for me. I don't play games on it, though I do use the camera now and again.
One slightly unusual task is tethering. When my internet goes down on my computers at home, the mobile network is often still available, so I tether my desktop to the phone connection. Visible will slow the connection speed tremendously, so I use an app that disguises the tether connection, and I get full speeds. So I need this app to work when the main internet connection goes wonky.
One year and eight months without security updates makes me a little more cautious about using the phone for anything online. I don't use it for bank accounts or credit cards, no instant payments of any kind, and there are no passwords saved within it. Even if I still got updates, I wouldn't use it for any type of financial transactions. I don't even check email with it.
In reality, a dumb phone would probably work for me, but Visible is notoriously picky about Android phones they will accept. And I don't use Apple for anything. No plans to change that.
I have been more and more interested in ditching Google software. I was recently forced to switch to Google Messages, since Samsung is turning their messaging app out to pasture. A Pixel 10a with GrapheneOS is something I'm considering. Visible will accept any modern Pixel phone, so they aren't a problem.
The question is, is any change necessary with how little I use the phone online? Perhaps I should just wait till the battery dies, but that doesn't help me in my efforts to de-Googlize.
Given your priorities, either go ahead and make the change to an pixel 10a, or buy a refurbished even cheaper/older pixel phone that supports Visible and GrapheneOS.
Sometimes we can't avoid a certain company and the only one we're beating up is ourselves. We can aim for "less dependence on" instead of "totally clean and free from". Let time do its thing. For example IBM eventually became a non-essential part of corporate landscape, and one day soon so will Microsoft. Aim for a refurbished unit so they don't get your money is probably good enough as far as sheer hardware goes. With the money saved you can also switch to another phone that perfectly fits your criteria should one appear.
As long as the battery is good and can use the functions you want to. I don't see why you have to buy a new one.