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

}
    return NullUniValue;
}
static const CRPCCommand commands[] =
{ 
  
    { "blockchain",         "getblockchaininfo",      &getblockchaininfo,      true  },
    { "blockchain",         "getbestblockhash",       &getbestblockhash,       true  },
    { "blockchain",         "getblockcount",          &getblockcount,          true  },
    { "blockchain",         "getblock",               &getblock,               true  },
    { "blockchain",         "getblockhash",           &getblockhash,           true  },
    { "blockchain",         "getblockheader",         &getblockheader,         true  },
    { "blockchain",         "getchaintips",           &getchaintips,           true  },
    { "blockchain",         "getdifficulty",          &getdifficulty,          true  },
    { "blockchain",         "getmempoolancestors",    &getmempoolancestors,    true  },
    { "blockchain",         "getmempooldescendants",  &getmempooldescendants,  true  },
    { "blockchain",         "getmempoolentry",        &getmempoolentry,        true  },
    { "blockchain",         "getmempoolinfo",         &getmempoolinfo,         true  },
    { "blockchain",         "getrawmempool",          &getrawmempool,          true  },
    { "blockchain",         "gettxout",               &gettxout,               true  },
    { "blockchain",         "gettxoutsetinfo",        &gettxoutsetinfo,        true  },
    { "blockchain",         "verifychain",            &verifychain,            true  },
    
    { "hidden",             "invalidateblock",        &invalidateblock,        true  },
    { "hidden",             "reconsiderblock",        &reconsiderblock,        true  },
    { "hidden",             "waitfornewblock",        &waitfornewblock,        true  },
    { "hidden",             "waitforblock",           &waitforblock,           true  },
    { "hidden",             "waitforblockheight",     &waitforblockheight,     true  },
};
void RegisterBlockchainRPCCommands(CRPCTable &t)