FWIW SARS-CoV-1 specific antibodies last approximately 3 years or so [1]. The antibody test all have a very high specificity (all I've seen have been 98%+, but I'm going off of memory and not any specific cited information), so you'll for sure know you had it.

[1]. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2851497/