Help with timelines

[2015gmailgreenwich]

I know this is similar to most of the other questions in the thread but there are a few wrinkles I haven't seen while glancing quickly that have me curious about what to do.

- I arrived in the UK on April 6 2015 on a fiance visa and got married on April 15 2015
- Had my appointment at a premium visa service center and received my visa on April 17 2015, therefore expiring on Oct 17 2017
- My wife and I (stupidly) booked a vacation in South America from Oct 12 to 23 this year, meaning that I will need my passport back by that date and presumably will need to complete the process before we go so I can re-enter the country
- I intend to continue living in the UK and apply for ILR after the next 30 month period

So given those dates, on what date should I apply for renewal such that it will
1. not expire too soon 30 months from now and require me to get a third FLR
2. not expire too soon 30 months from now so that I've lived here long enough to apply for ILR
3. given all of this, I plan on making another booking at a premium visa service center. However, the only one near me is in Croydon. Given that you can only apply 28 days in advance but can make appointments 42 days in advance, I am nervous that the center will run out of appointments. Is this something that often happens and how do people deal with it?

I really hope we don't have to move our non-refundable vacation, but obviously staying in the UK is more important. Any help is appreciated.

[New on forum]

I know this is similar to most of the other questions in the thread but there are a few wrinkles I haven't seen while glancing quickly that have me curious about what to do.

- I arrived in the UK on April 6 2015 on a fiance visa and got married on April 15 2015
- Had my appointment at a premium visa service center and received my visa on April 17 2015, therefore expiring on Oct 17 2017
- My wife and I (stupidly) booked a vacation in South America from Oct 12 to 23 this year, meaning that I will need my passport back by that date and presumably will need to complete the process before we go so I can re-enter the country
- I intend to continue living in the UK and apply for ILR after the next 30 month period

So given those dates, on what date should I apply for renewal such that it will
1. not expire too soon 30 months from now and require me to get a third FLR
2. not expire too soon 30 months from now so that I've lived here long enough to apply for ILR
3. given all of this, I plan on making another booking at a premium visa service center. However, the only one near me is in Croydon. Given that you can only apply 28 days in advance but can make appointments 42 days in advance, I am nervous that the center will run out of appointments. Is this something that often happens and how do people deal with it?

I really hope we don't have to move our non-refundable vacation, but obviously staying in the UK is more important. Any help is appreciated.

You can apply anytime in last 28 days of your current visa .
Book premium service for any time 3 weeks before expiry date and make sure you take all the documentation with you otherwise you are most certainly going to cancel your vacation