It takes from 5 (shortest) to almost 40 (longest) minutes for `bitcoin-cli gettxoutsetinfo` to return an _empty_ dict. I noticed this first whilst configuring the Statoshi branch of Bitcoin Core, but went back to install Bitcoin Core (git clone -b v0.11.2 https://github.com/bitcoin/bitcoin.git) to find the same results.

```
20:10 pi@raspinode:~/bin/bitcoin.orig $ bitcoin-cli gettxoutsetinfo
{
}
20:12 pi@raspinode:~/bin/bitcoin.orig $ bitcoin-cli getinfo
{
    "version" : 110200,
    "protocolversion" : 70002,
    "blocks" : 393193,
    "timeoffset" : 0,
    "connections" : 12,
    "proxy" : "",
    "difficulty" : 113354299801.47113037,
    "testnet" : false,
    "relayfee" : 0.00005000,
    "errors" : ""
}
20:17 pi@raspinode:~/bin/bitcoin.orig $
```

Raspberry Pi 2 - 1GB memory - 4 core CPU 900MHz - Blockchain on SanDisk Ultra Android microSDXC 128GB up to 80 MB/Sec Class 10

All other RPC calls through bitcoin-cli are answered promptly and correctly.
See also issue on jlopp/statoshi https://github.com/jlopp/statoshi/issues/19#issuecomment-171350739

+ HelpExampleCli("gettxoutsetinfo", "")
            + HelpExampleRpc("gettxoutsetinfo", "")
        );
    UniValue ret(UniValue::VOBJ);
    CCoinsStats stats;
    FlushStateToDisk();
    if (GetUTXOStats(pcoinsTip, stats)) {
        ret.push_back(Pair("height", (int64_t)stats.nHeight));
        ret.push_back(Pair("bestblock", stats.hashBlock.GetHex()));
        ret.push_back(Pair("transactions", (int64_t)stats.nTransactions));
        ret.push_back(Pair("txouts", (int64_t)stats.nTransactionOutputs));
        ret.push_back(Pair("bytes_serialized", (int64_t)stats.nSerializedSize));
        ret.push_back(Pair("hash_serialized", stats.hashSerialized.GetHex()));
        ret.push_back(Pair("total_amount", ValueFromAmount(stats.nTotalAmount)));
    }
    return ret;
}
UniValue gettxout(const UniValue& params, bool fHelp)
{
    if (fHelp || params.size() < 2 || params.size() > 3)
        throw runtime_error(
            "gettxout \"txid\" n ( includemempool )\n"
            "\nReturns details about an unspent transaction output.\n"
            "\nArguments:\n"
            "1. \"txid\"       (string, required) The transaction id\n"
            "2. n              (numeric, required) vout number\n"
            "3. includemempool  (boolean, optional) Whether to include the mem pool\n"
            "\nResult:\n"
            "{\n"
            "  \"bestblock\" : \"hash\",    (string) the block hash\n"