According to Odaily Planet Daily, Vitalik said in the Reddit sub-forum that the current budget strategy of the Ethereum Foundation (EF) is to spend 15% of the remaining funds each year, which means that EF will last forever, but as part of the ecosystem it will become smaller and smaller over time.
Earlier news, Justin Drake of the Ethereum Foundation said that EF's financial report will be released soon. EF spends about $100 million a year. At current prices, EF's main Ethereum wallet is worth about $650 million.