I actually suggest looking for a job even if everything is going smooth at your current company.
( yeah well, i dont mean you do a job interview every week - but even having workend in the same company for 8 years now, I normally got through at least 2 interview processes a year.

1. it keeps you trained- interviews are stressful situations, you have to become comfortable in presenting yourself, answering tricky HR questions, doing coding challenges or whiteboard exercises, and so on. I'd rather do that when I am relaxed for my current economic and professional situation, rather that doing that when I am depressed for having being fired, or frustrated because i am not happy anymore and stressed that if i dont pass i could have problems making the ends meet.
2. it gives you a reality check. what is the market looking for, are you still uptodate, are your skills still relevant, what is the salary you can get elsewhere, how much salary raise could you eventually ask in your next feedback talk? It's easy to get too comfortable when you work for a company long enough.
3. you get used to ghosting and rejections without too much emotional load. unfortunately there are still many companies and recruiters that at first are all emails and phone calls and compliments and then disappear when they found someone else . Rejections are part of the process, you might understand that you must update your game, or you can just learn that simply because someone was a better fit it doesnt mean that you suck.
4. you are not married to a company. you don't have to wait for your partner to ask for a divorce (or leave you after they had an affair) to start dating someone else :-)
5. you might fall in love with your company over and over again. and realize that it's the best place to work at, you get paid well and the projects you are working on are interesting and challenging, as much as those of that cutting edge revolutionary startup...
6. you might catch the right opportunity at the right time, Success is sometimes a matter of a bit of luck and timing. or you might be able to get a raise if you announce you are leaving ( when it is really true, don't bluff) if you are a valuable player for your team/company.

The positive side of having interviews every now and then is that you must take them seriously ( don't just waste other people time nor throw yourself into embarassing situatiuons) without taking them too seriously.

First and foremost is the considerations of "vulnerability". In the US, if you are laid off you may be eligible for unemployment. If you quit, that's off the table. Also, there's likely a window of time when start a job when you are not eligible for unemployment. So quitting and starting a new job may remove the "unemployment benefit" option.

There's also a trend of rescinding offers. What happens if you put in your notice, formally resign, and the place you jump to rescinds the offer?

How I like to think about situations where I'm on the fence is to ask myself "What can I learn in this moment that will help me take my next step?"

That can be taking on a higher profile project at your current ; a project with more responsibility. From that activity, you can learn skills but also listen to your "heart"; do you have energy to keep doing that in your current company?

But by all means, if you're worried, concerned, want to practice, not feeling it, then start the interview process. At a minimum it's practice.