This is all a question of how you define things.

Firstly the problem is defining languages. Do you define them so that Serbo-Croat is still one language or six, for example? Is Malay and Indonesia a separate language? What about the languages of India, and Africa, where there are many mutually partly intelligible languages. Is Flemish and Dutch one language or two in the way you are defining it? In my opinion it is better to define these broadly and cut it down to a smaller number of claimed languages. After all, where do you stop? Maybe American and British English could be claimed as two – I heard some people try that, ridiculous though it is.

Secondly, there is the problem of desired fluency. A person who only needs to say certain fixed sentences, like a street seller or a receptionist, can say what they know with fluency, but they are not able to synthesis accurate language. Others can do so, but not in speaking as they never mastered it. I tend to go on passive vocabulary learned and put 10,000 as a very reasonable target for learning a language.

Thirdly, you need to define “lifetime”. You don’t know yet how long you will live, nor whether you will still be so keen on learning languages if it is to the detriment of learning other useful things. The day may come – and does to many a polyglot (this is why most of the older polyglots you meet are people who leave it and come back to it – or old people who used to be polyglots but have not studied actively for a long time) where you say “instead of learning Javanese, I think it’s time to learn Java”.

If a person uses optimal methods and gives 400 hours to each language, then if they study for 40 years at 20 hours a week, 50 weeks a year, they’ll have given 400 hours each to 100 languages. With good methods, that should mean the ability to demonstrate reasonable proficiency at least in the reading of those 100 languages. One might choose to spend the same time doing 4,000 hours each to only 10 languages, and show a high degree of fluency in just those ten languages. One might also go down the performing seal route and do 40 hours on a thousand languages just in order to be able to recognise maybe a thousand words and in some cases read or write very basic words in those 1,000 languages. Here one of your biggest problems is going to be materials. Which ever way you cut it, 40,000 hours of study is a large achievement, and it is really up to whether the learner has more utility for what he or she wants from their study whether to be more academic on a smaller number or more hobbyist on a larger number.