Dear Worried Girl,
Here are the reasons that I would tread lightly on becoming best friends with an old love.
Reconnecting with an old flame may create excitement in your life and make you lose your perspective. This can allow you to forget what caused your break-up in the first place.
You may dream of all the good times you had with your old flame, and forget about the bad times. This may make you restart the old relationship, forgetting about your present relationship with your spouse.
The feelings you once held for your old love may still be present, and despite your wish to maintain a platonic friendship, you may be unable to do so.
On the whole, an old flame is just an "old flame" - a relationship that has outlived its worth and is best left alone.
Of course these are just my thoughts and reactions and you must make your own choices after looking at renewing the friendship from all angles. I am sure you will do what you feel is best for you. (((((Hugs)))))))
With kindest personal regards,