The asymptotic behavior is given for the error rates and ASN of the Wald SPRT and of invariant sequential tests. An asymptotic justification of Bhate's conjecture is also provided for invariant sequential tests. Expressions are obtained for the asymptotic relative efficiency of the Wald SPRT as compared with the corresponding best non-sequential test.
"Some Asymptotic Aspects of Sequential Analysis." Ann. Statist. 1 (6) 1126 - 1138, November, 1973. https://doi.org/10.1214/aos/1176342561