Diet Coke Syrup

I’m new to adding bubbles at home and a have a question about the Diet Coke syrup.

A quick search showed me two options online; the 5 gallons bib at Costco and a 2L/4L bottle from SodaCentre.

While I drink Diet Coke almost every day, a 5 gallon would take me a long time to drink. I’m assuming here that it is actually 5 gallons of syrup, and not soda, and I usually will drink 12oz per day. Since these syrups expire, I’m leaning towards the 2L bottle from SodaCenter, but I haven’t heard anyone using it in the past.

Have you ever bought Coke syrup for using it with your soda machine at home? Which Coke syrup did you buy? What was your experience with it? Would you recommend someone buying it? Have you tried the syrup bottles from Soda Center?