Sydney Airport transfer, from T1 international to T3 domestic

Arriving SYD at 10 a.m. weekday international then connect to QF T3, one ticket/PNR with checked luggage  I have 3 hours to do this, but am concerned if that's enough given my review on other sites about the length of clearing immigration and customs/quarantine process.  I had envisioned having lunch at the QF business lounge and don't know now if I will be able to do that.  I'm on MH and have noticed that this flight on occasion uses the remote parking and then it's a bus trip to the T1 terminal.  Adding it all in, including the QF bus trip to T3, I believe 3 hours might not be enough.  Anyone with experience having landed at that time at T1?  I will have to declare my prescription medicines, so that should cost dearly in time at customs.  It seems Sydney airport is on par now with London Hearthrow where it can take upwards to 5 hours to get through the process during peak times, season.

I would think 3 hrs is plenty at that time and at any time for transfers in Sydney. Sydney airport is bad, but not bad enough to consume 3 hrs of your life. Obviously, get the machine to spit out your immigration ticket as soon as you find one walking towards immigration and use the kiosks to clear immigration. Have the medicine handy to show to customs (if required).

Is 10am peak time being as all the big birds land at 6am?

As above 3 hours seems like more than enough time to transfer through Sydney even in very busy times. Two tips. There are customs agents that circulate around the baggage claims area, so feel free to approach and talk to them about the medicine as they may decide that you don't need to declare it prior to you needing to line up. Second tip is that once you have cleared customs locate the Qantas domestic transfer desk in T1 (I believe it is well signed) In my previous experience they've been very good at adapting to delays from international to domestic especially if you are on the same PNR (I imagine it happens a lot) They'll re-check your domestic luggage and put you on the bus that runs between the international and T3. The bus drop's you airside in T3 and from there it's a relatively short walk to most of the gates (ie less than 10 minutes at normal walking pace)

My mate took the same MH flight from KL then transited through SYD to BNE. Despite parking on the remote stand it took him about 1.5 hours from landing until he emerged from the domestic T3 bus drop off, whilst this is likely best case, it can be done. Personally I'd consider loopflyers post above as more of a worse case scenario. Qantas will put you on the next flight going to your onward destination if you really get held up.

I regularly make international to domestic connections at Sydney with under 2 hour connection times and still have heaps of time in the lounge. If the inbound flight is severely  delayed I have missed my connection but Qantas has simply booked me on the next flight I can make.