A player of Pokemon Trading Card Game Pocket figured that completing the first set, Genetic Apex can take around two years if one does not spend money to buy the cards.
A Reddit post from TCGPCollector explained the different methods of collecting cards and their completion times. He revealed the most efficient way to collect all 286 cards for free would require 655 days.
Simulating how many days it would take to get a complete collection (WITH GRAPHS!)
byu/TCGPCollector inPTCGP
The primary completion of the set requires 226 cards. This means the required 655 days time includes the 60 alternate art cards as well, which can be daunting and more time-consuming since they need the unreliable Wonder Pick feature for it. In this feature, the players need to log in every day and access the card they need.
Therefore for players for whom it is a hard pass, it would require less than 655 days to complete their collection.
The timeframe of two years will also not apply to the players who will use a future trading feature that is still undated. This trading feature will allow the players to exchange their cards with other players especially for the last few cards to complete their set. This will save the players from the randomness of the Wonder Pick feature.
Additionally, those owning the Premium Pass at $9.99 a month can collect every card in 437 days. However, the cost of the pass will total up to $150 during this time which is quite a lot.
Players who are not too excited about the alternate art cards can complete the collection with regular ones in just about 130 days. This can be further reduced to 87 days with a Premium Pass.
The developer of Pokemon TCG, Creatures Inc will expectedly release a new collection of 200 to 300 cards every 3 to four months. This means the active players will be able to finish one set before the next set is released.