Robin W

This Plugin changes the ‘freshness ‘ that bbPress displays on topic and forum lists (eg 4 hours ago) to the date of the last post to that forum or topic (eg 17th January 2014 at 5.15pm).
It also allows you to set the heading for this new date format.
The existing (bbpress) Recent Topics widget works with date, but a revised Recent Replies Widget to display the date format called (Last Post) Recent Replies is included.

bbp last post

After trying to code things myself (to keep the number of plugins down), I found it easier simply to install this.

Very happy, it works perfectly

For bbPress - changes the freshness displays to date

dFactory

<a href="http://www.dfactory.eu/plugins/bbpress-notifications/" rel="nofollow ugc">bbPress Notifications</a> allows you to automatically send email notifications to specific users when new topics or replies are posted. It integrates seamlessly into WP, by adding new section to bbPress settings page, where you can configure your notifications.
For more information, check out plugin page at <a href="http://www.dfactory.eu/" rel="nofollow ugc">dFactory</a> or plugin <a href="http://www.dfactory.eu/support/forum/bbpress-notifications/" rel="nofollow ugc">support forum</a>.
<h4>Features include:</h4>
<ul>
<li>Send notification when New Topic is published</li>
<li>Send notification when New Reply is published</li>
<li>Specify email addresses for notifications</li>
<li>Design email templates with a number of shortcodes</li>
<li>Available shortcodes: [blogname], [reply-title], [reply-content], [reply-excerpt], [reply-url], [reply-author], [topic-title], [topic-url], [topic-author]</li>
<li>.pot file for translations included</li>
</ul>

bbPress Notifications

bbPress Notifications allows you to automatically send email notifications to specific users when new topics or replies are posted.

bbp last post vs bbPress Notifications