Yes, there is still a time frame for earning curation rewards, but it works differently from the old days.

The old system had a "reverse auction" period that reduced curation rewards when voting immediately after publication. It was originally 30 minutes, later reduced to 15 minutes and then 5 minutes. Since Hardfork 25, that reverse-auction period has been completely disabled. Therefore, voting on a post that is only a few minutes old does not penalize your curation reward.

Under the current rules:

• During the first 24 hours, your vote receives its full calculated curation weight.
• From 24 to 72 hours, the curation weight is divided by 2.
• After 72 hours, it is divided by 8.
• The post pays out after approximately 7 days, so votes after payout do not earn curation rewards.

The blockchain code explicitly applies these reductions based on the age of the post.

Regarding other people voting after you: your curation weight is calculated when you vote, based on how much reward weight your vote adds at that moment. Later votes do not retroactively recalculate your weight. However, they can increase the post’s total payout and also add more curation weight that must share the curator portion.

At payout, the available curation reward is divided among voters according to:

your vote weight ÷ total vote weight of all curators

So voting before a post becomes popular can generally give you a larger relative share than casting the same vote after many large votes have already arrived. But voting extremely early is also a gamble: if nobody else supports the post, its total payout—and therefore the curator reward pool - may remain small.

So the practical answer is: you no longer need to wait 30 minutes - or even 5 minutes. Voting within the first 24 hours receives full timing weight and being early on content that later attracts substantial votes can be beneficial.