This is speculation, as this is not what the requirement says, explicitly or implicitly. When in doubt, you have to fall back on what the text says, and here it's: "at the time of application", nothing more. As written, I see it as the applicant providing proof that he/she is solvent at the level that constitute "wealthy" for the purpose of the LTR. I may well be wrong, but I haven't asked the BOI because it's not my case (yet).
The requirement for medical insurance is "at least 10 months" at the time of application. Here again ,there is no explicit or implicit requirement to maintain coverage after that time. I agree though that for those using the 100K, it's a question to clarify with the BOI, but rules have changed before and they may change again within 5 years.