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

obj.push_back(Pair("headers",               pindexBestHeader ? pindexBestHeader->nHeight : -1));
    obj.push_back(Pair("bestblockhash",         chainActive.Tip()->GetBlockHash().GetHex()));
    obj.push_back(Pair("difficulty",            (double)GetDifficulty()));
    obj.push_back(Pair("mediantime",            (int64_t)chainActive.Tip()->GetMedianTimePast()));
    obj.push_back(Pair("verificationprogress",  Checkpoints::GuessVerificationProgress(Params().Checkpoints(), chainActive.Tip())));
    obj.push_back(Pair("chainwork",             chainActive.Tip()->nChainWork.GetHex()));
    obj.push_back(Pair("pruned",                fPruneMode));
    const Consensus::Params& consensusParams = Params().GetConsensus();
    CBlockIndex* tip = chainActive.Tip();
    UniValue softforks(UniValue::VARR);
    UniValue bip9_softforks(UniValue::VOBJ);
    softforks.push_back(SoftForkDesc("bip34", 2, tip, consensusParams));
    softforks.push_back(SoftForkDesc("bip66", 3, tip, consensusParams));
    softforks.push_back(SoftForkDesc("bip65", 4, tip, consensusParams));
    BIP9SoftForkDescPushBack(bip9_softforks, "csv", consensusParams, Consensus::DEPLOYMENT_CSV);
    BIP9SoftForkDescPushBack(bip9_softforks, "segwit", consensusParams, Consensus::DEPLOYMENT_SEGWIT);
    obj.push_back(Pair("softforks",             softforks));
    obj.push_back(Pair("bip9_softforks", bip9_softforks));
    if (fPruneMode)
    {
        CBlockIndex *block = chainActive.Tip();
        while (block && block->pprev && (block->pprev->nStatus & BLOCK_HAVE_DATA))
            block = block->pprev;
        obj.push_back(Pair("pruneheight",        block->nHeight));
    }
    return obj;
}
struct CompareBlocksByHeight
{
    bool operator()(const CBlockIndex* a, const CBlockIndex* b) const