Not to be the cash Nancy but at the moment there is some merit to putting a bit of the windfall away in a term deposit or higher interest savings account. A windfall is a windfall and not knowing anything else about your financial position a nice little buffer there can serve as a wonderful psychological booster. Yes, inflation but hey if you throw it all into the market and everything drops 15% then take another 8% off that too. Ya get me? (not my position IRL though I am almost 100% invested)
Still means you can average in but unless you have a deep knowledge on where to "place your bets" you can probably take advantage of volatility towards the downside if and when better opportunities present themselves to you rather than going "Ah, crap. All my big money is gone".
I do like the idea that you're not thinking about going and buying a used Porsche. (unless it's a 70's Targa, in which case hit me up. I want to go for a drive)
From personal experience recently, I had a Ranger that I had purchased outright and thanks to Covid prices was still worth every cent I paid for it 3 years ago. So I saw it sitting parked out the front 5 days a week as I was only using it on weekends and decided I would rather have the money in my pocket. Still needed something to fill with tools and do tip runs while we do some work on the house but was able to get a much cheaper van that does 90% of the same job but with a little less comfort. Put $40k back in my pocket and I probably held on to most of it for about 6 months but gradually fed into the market, especially around those wild times where people were selling heavily into tax time (presumably to lock in some losses) and have had some wonderful short-term boosts. 10/10 would do it again as everything I bought I planned to keep for 2+ years but was happy to take a 3-month 30% jump in some.
You do you, but since interest rates are no longer 0.85% for a term deposit, I would seriously be considering a nice cash buffer of 20-50% of the windfall at this point in time. Dry powder could be a wonderful resource in the next 24 months.