The difference may be more in how they’re intended to be used rather than their relative strength. Conformal Coating Remover XT (part #2130) is slower evaporating so on larger surfaces it will probably be more effective. It will reside on the board longer and therefore able to soften, penetrate and lift coatings. Fast evaporators may not be as effective over larger areas because they would tend to evaporate too quickly and redeposit the coating. 2130 is also much lower toxicity, so safer to use when ventilation is poor. Fine-L-Kote Conformal Coating Remover (#2510) is faster and probably more tuned for smaller areas or spot removal, which is why it’s the formula offered in the pen.
The shelf life of a product can be found on either the technical data sheet (TDS), available on the product page, or by looking on the certificate on conformance (COC). The COC can be downloaded by going to https://www.techspray.com/coc. Once you have the shelf life, you will need to add it to the manufacture date for a use-by date. The manufacture date can be identified by the batch number. The batch code used on most of our products are manufacture dates in the Julian Date format. The format is YYDDD, where YY = year, DDD = day. For example, 19200 translates to the 200th day of 2019, or July 19, 2019. This webpage explains and provides charts to help interpret our batch numbers: https://www.techspray.com/batch-codes.