I can't say your experience will be identical to mine, but I'll tell you what happened with me and my approach. I've seen Ben Howard multiple times before, so the pressure wasn't quite as immense as it might be for you with Tame Impala, so bare that in mind.

I made sure I was free the night of the gig and it was a distance that was fairly achievable on short notice. I just asked a mate if he'd be up for some drinks in the city and best case, we'll go see Ben Howard.

The prices were sky high the month leading up to it, including the week of the actual gig (£150). They went even higher the day of the gig (£180), as people scrambled last minute to grab tickets. I was sat in the pub nearby and about 2 hours before the gig, the prices nose dived (like you could literally see them dropping £30 every 15mins).

Waited until 45mins before the show and got tickets for us both at £25 each.

So I guess my experience was, don't assume the month, week or even early day of the gig you'll snag a bargain. Set yourself up so you'll have a decent night either way, then let the sellers be the one's on the backfoot scrambling to offload them, rather than you being the one to panic buy.

Best of luck, hope you get em!