Clients tend to have similar questions no matter what their industry is. Websites are similar in many ways and there are several topics that clients ask about either before or during their project.
Opening in the same tab is considered a UX best practice because it allows the back button to work and for browser history to be linear. Opening in a new tab is just as much of an impediment to someone returning to your site as having to click "back" (think of how often you actually go through and click on each individual tab you hit in your session). Especially when you think about mobile, it’s way easier for the user to go "back" to the previous site than for them to hunt down the original tab. So there’s much more of a chance that you lose a mobile user forever if you make a link open in a new tab. It can also throw "time on site" metrics for a loop since the user is technically still on your site while they are using other tabs. Most browsers pause JS execution for inactive tabs but they might briefly re-activate it when they go to close it later, which can make your stats inaccurate. Finally if you set your links to just be regular links, users who want a new tab can make that happen with a control-click, but the reverse is not true. If someone wants the link to open in the same window and you set it to open in a new one, they don’t have a choice. So we prefer to let the user decide how they want to browse and trust that if we are accommodating of their preferences they will look more favorably upon usGood discussion of the issue here: smashingmagazine.com/2008/07/should-links-open-in-...
If a warranty fix comes up, re-open the project. Add a "Post-launch work" task. It should be billable, as we would bill for it if the project were hourly. In the case of a fixed bid project the warranty means the client gets it for free but it’s still considered billable from our perspective. Keep the project open while we perform the update. When it is successfully QAed and launched, close the project again.