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 (consensusParams.vDeployments[id].nTimeout > 0)
        bip9_softforks.push_back(Pair(name, BIP9SoftForkDesc(consensusParams, id)));
}
UniValue getblockchaininfo(const UniValue& params, bool fHelp)
{
    if (fHelp || params.size() != 0)
        throw runtime_error(
            "getblockchaininfo\n"
            "Returns an object containing various state info regarding block chain processing.\n"
            "\nResult:\n"
            "{\n"
            "  \"chain\": \"xxxx\",        (string) current network name as defined in BIP70 (main, test, regtest)\n"
            "  \"blocks\": xxxxxx,         (numeric) the current number of blocks processed in the server\n"
            "  \"headers\": xxxxxx,        (numeric) the current number of headers we have validated\n"
            "  \"bestblockhash\": \"...\", (string) the hash of the currently best block\n"
            "  \"difficulty\": xxxxxx,     (numeric) the current difficulty\n"
            "  \"mediantime\": xxxxxx,     (numeric) median time for the current best block\n"