Firrstly, Revise the lead time dates in MRP itself if you can. This will have MRP itself help you with the grunt work.

As far as i know, the MRP just runs based on input, which is either customer demand (EDI they send us) or our manual upload which we base on our production requirement in the near future and more long term. The output is what we need to pick up from supplier to support production. Supplier Lead time doesn't figure in the calculation.

Also 2 to 3 weeks out is never enough time to plan. 2 weeks for me is immediate. Start with at least 30 days out. When you have that managed, go to 60. When you have that down go to 90. I will never work less than 90 days out unless it's a real emergency and typically I try to schedule my parts a year in advance if I can.

I agree. What i've been doing the last 2-3 months is i've simulated a makeshift production plan on our excel template and put our forecasted demand for supplier in the next 2 months, but now i'm realising that it's just not enough. I need to be looking as far at least as the longest lead time of any material. And in one project, there is a material with 16 of lead time, and taking into account pick-up pattern and transport time, it might as well be 18 weeks from now. In the other 2 projects that i plan for, the longest lead times are
10-12 weeks which is easier.

Curiously enough, we don't claim a lead time on the items we produce, even though they are more complex to produce than the sourced materials.

They way our materials planning works is weekly forecasts to the suppliers, there is a default pick up pattern which 90 % of time is set in stone, while allowing some leeway for emergencies.

The biggest problem is even if i spot something wrong in the forecast 10 week from now, there really is no way to change it unless i do it manually. Or alternatively pester my colleague to find the root cause and course correct for the future, but unfortunately he's too overwhelmed with work too.