If I unlock an encrypted wallet for 359711509437336256 or less seconds, I can sign transactions with it:

    $ bitcoin-cli walletpassphrase "$x" 359711509437336256
    $ echo $?
    0
    $ bitcoin-cli signrawtransaction $tx | grep complete
      "complete": true

But if I unlock it for 359711509437336257 or more seconds, it appears to have unlocked but I can't sign any transactions:

    $ bitcoin-cli walletpassphrase "$x" 359711509437336257
    $ echo $?
    0
    $ bitcoin-cli signrawtransaction $tx | grep complete
    error code: -13
    error message:
    Error: Please enter the wallet passphrase with walletpassphrase first.

I don't know the significance of that number. It's nowhere near a power of 2.

I was trying to unlock the wallet effectively "forever", so put a big number. If I use too big a number (2^63 or more) I get an error message `JSON integer out of range` but for numbers between 359711509437336257 and 2^63-1 inclusive I get no error, but no actual unlocking.
+ HelpExampleRpc("rescanblockchain", "100000, 120000")
            );
    }
    LOCK2(cs_main, pwallet->cs_wallet);
    CBlockIndex *pindexStart = chainActive.Genesis();
    CBlockIndex *pindexStop = nullptr;
    if (!request.params[0].isNull()) {
        pindexStart = chainActive[request.params[0].get_int()];
        if (!pindexStart) {
            throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid start_height");
        }
    }
    if (!request.params[1].isNull()) {
        pindexStop = chainActive[request.params[1].get_int()];
        if (!pindexStop) {
            throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid stop_height");
        }
        else if (pindexStop->nHeight < pindexStart->nHeight) {
            throw JSONRPCError(RPC_INVALID_PARAMETER, "stop_height must be greater then start_height");
        }
    }
    
    if (fPruneMode) {
        CBlockIndex *block = pindexStop ? pindexStop : chainActive.Tip();
        while (block && block->nHeight >= pindexStart->nHeight) {
            if (!(block->nStatus & BLOCK_HAVE_DATA)) {
                throw JSONRPCError(RPC_MISC_ERROR, "Can't rescan beyond pruned data. Use RPC call getblockchaininfo to determine your pruned height.");
            }
            block = block->pprev;
        }