With the current pace of the patches you could consider a target time of at least 18 months since the only major update is 5.0, the others don't have as many additions as this one until 5.7/6.0 that add much more still. If I remember correctly the price in the official was 10,000 credits so I do not know if here will maintain that or be more expensive but with the current price of 1.6-2.0k of gold for 1k of credits can be relatively easy to collect 10k of credits
The time estimate is based on previous patches and considering variations in the addition of new events, missions, skillset arrangement among other things