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

};
static bool GetUTXOStats(CCoinsView *view, CCoinsStats &stats)
{
    std::unique_ptr<CCoinsViewCursor> pcursor(view->Cursor());
    CHashWriter ss(SER_GETHASH, PROTOCOL_VERSION);
    stats.hashBlock = pcursor->GetBestBlock();
    {
        LOCK(cs_main);
        stats.nHeight = mapBlockIndex.find(stats.hashBlock)->second->nHeight;
    }
    ss << stats.hashBlock;
    CAmount nTotalAmount = 0;
    while (pcursor->Valid()) {
        boost::this_thread::interruption_point();
        uint256 key;
        CCoins coins;
        if (pcursor->GetKey(key) && pcursor->GetValue(coins)) {
            stats.nTransactions++;
            ss << key;
            for (unsigned int i=0; i<coins.vout.size(); i++) {
                const CTxOut &out = coins.vout[i];
                if (!out.IsNull()) {
                    stats.nTransactionOutputs++;
                    ss << VARINT(i+1);
                    ss << out;
                    nTotalAmount += out.nValue;
                }