A tough question for without prying too much into your financial situation, I'm assuming you are looking for a job out of need rather than because you want to feel like a contributing employee again. While I cannot answer this question for you as I am not you, you've already mentioned several key factors in your question as to why you shouldn't go back to your old job.

For one thing, you implied in your question that your previous employers have not said yet whether they want you back. As they are hiring, there may be a chance that they want younger people who are inexperienced in the job: hence they can mold them into the type of employee they want the candidate to be.

No disrespect but in the 7 years since you left, you have probably changed somewhat and so are no longer the desirable employee that you once were. In fact you even mention how you have less energy now than you did back then: implying that the job has a somewhat physical aspect to it.

From what you have mentioned, I would personally move on and seek work in a different company instead of with your former employers. It is often forgotten but there is more to a job than just the paypacket you bring home and the friends you may make at work. There are also the new skills and abilities that you will develop at the job.

Unfortunately if you were to take up the old io again, the chances are you won't be developing any new skills or abilities but simply relearning the ones you covered before. As such you won't be developing as a person.

If you want to discuss this further and help going forwards, why not book me in for a consultation.