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

{
        if (!chainActive.Contains(item.second)) {
            setOrphans.insert(item.second);
            setPrevs.insert(item.second->pprev);
        }
    }
    for (std::set<const CBlockIndex*>::iterator it = setOrphans.begin(); it != setOrphans.end(); ++it)
    {
        if (setPrevs.erase(*it) == 0) {
            setTips.insert(*it);
        }
    }
    
    setTips.insert(chainActive.Tip());
    
    UniValue res(UniValue::VARR);
    BOOST_FOREACH(const CBlockIndex* block, setTips)
    {
        UniValue obj(UniValue::VOBJ);
        obj.push_back(Pair("height", block->nHeight));
        obj.push_back(Pair("hash", block->phashBlock->GetHex()));
        const int branchLen = block->nHeight - chainActive.FindFork(block)->nHeight;
        obj.push_back(Pair("branchlen", branchLen));
        string status;
        if (chainActive.Contains(block)) {
            
            status = "active";
        } else if (block->nStatus & BLOCK_FAILED_MASK) {
            
            status = "invalid";