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

fMempool = params[2].get_bool();
    CCoins coins;
    if (fMempool) {
        LOCK(mempool.cs);
        CCoinsViewMemPool view(pcoinsTip, mempool);
        if (!view.GetCoins(hash, coins))
            return NullUniValue;
        mempool.pruneSpent(hash, coins); 
    } else {
        if (!pcoinsTip->GetCoins(hash, coins))
            return NullUniValue;
    }
    if (n<0 || (unsigned int)n>=coins.vout.size() || coins.vout[n].IsNull())
        return NullUniValue;
    BlockMap::iterator it = mapBlockIndex.find(pcoinsTip->GetBestBlock());
    CBlockIndex *pindex = it->second;
    ret.push_back(Pair("bestblock", pindex->GetBlockHash().GetHex()));
    if ((unsigned int)coins.nHeight == MEMPOOL_HEIGHT)
        ret.push_back(Pair("confirmations", 0));
    else
        ret.push_back(Pair("confirmations", pindex->nHeight - coins.nHeight + 1));
    ret.push_back(Pair("value", ValueFromAmount(coins.vout[n].nValue)));
    UniValue o(UniValue::VOBJ);
    ScriptPubKeyToJSON(coins.vout[n].scriptPubKey, o, true);
    ret.push_back(Pair("scriptPubKey", o));
    ret.push_back(Pair("version", coins.nVersion));
    ret.push_back(Pair("coinbase", coins.fCoinBase));
    return ret;
}
UniValue verifychain(const UniValue& params, bool fHelp)